Chapter 1: Night Flight
It was late fall, with the brilliant colors already turning dull. The leaves of the large chestnut close by our old stone house lay on the ground, curled and brown and brittle. The sky was overcast, but without definition -- no way to identify the clouds, it was simply gray and dreary.
I looked back as I turned the car from the dirt road onto the two-lane blacktop, and waved to my wife, Jean, who was watching me go; she waved back, and after that I only looked ahead.
I felt that emptiness and sadness I always faced when leaving home and family, the nagging feeling of not having had the time for all the important things to do or say.
The country road soon reached the Delaware River; after that the roads grew bigger, and the occasional auto became many as others slid into the flow. Finally the route became the steady nose-to-tail stream of highway leading to New York City and its disheartening surroundings. As home dropped back behind me and the airport loomed, the sad feeling retreated to a quiet place in the mind's back storage, while my primary thoughts turned to the evening's task.
This night I'd fly a Boeing 747 from New York across the Atlantic to Paris, as I did four or five times a month, hauling people, mail, and cargo -- a pleasant task despite the problems that weather, crew, and airplane might toss my way. Whenever I drove to an airport the same thoughts occupied my mind, mostly about emergencies and what I would do if one occurred.
The act of flying an airplane is a daily chore and I'd long since become proficient at it, the repeated reactions and movements automatic, but emergencies almost never happen so there's no rehearsal for them except for a few hours twice a year in a simulator. And that doesn't cover all of them -- ditching the plane in mid-Atlantic, for example. So you review these things, playing mental games of how to cope if the improbable should come true, and the time spent driving to the airport gives you a good opportunity to do it.
What if an engine catches fire? Pull back the throttle, cut the start lever, call for the emergency checklist. How necessary is this review? I'd been thirty years a captain and only had one fire, on a Constellation -- a "Connie" -- taking off from Frankfurt, Germany. Just as we broke ground there came the shattering confusion of a loud bell and a bright red light. "Engine fire!" Quick action on the remembered items: throttle closed, fuel mixture off, fire extinguisher lever pulled, "Read the engine fire checklist!" All the pre-trained, well-thought-out operational actions took place, right by the book. But in the back of my mind was the thought of a wing burning off, which told me, "Get the son of a bitch back on the ground as fast as possible."
I wrapped the plane into a tight turn I had learned long ago while flying fast around pylons in small-time air races and stunt shows. "Tell the tower we're coming right back," I said. The tower operator, accustomed to orderly traffic flow procedures, tried to direct us to follow another aircraft, a normal aircraft on a normal flight. A few firm words advised the tower to get others out of the way, that we were in a hurry for terra firma.
We landed okay -- total flight time was probably five or six minutes, and the fire was out before we touched down -- but it had been a fire, caused by a complicated turbine failing and tearing things up. Those few minutes presented the contrast of carefully taught and programmed reactions versus the kind of seat-of-the-pants flying you store up during long hours of flight time -- some call it "fright time," and a pilot needs some of that in his or her dossier. The modern way is right and necessary, but periodically there are difficult and perhaps emergency situations that demand the basic stick and rudder skills of quick, intuitive action.
But now it was time to quit thinking about that day in a Connie, and to come back to the 747 I was going to fly tonight. How about a hydraulic system loss? An electrical? Instruments? I go over each one -- and the tough ones, too, like a crash landing with fire, and how to get 400 people off the plane; review your actions, think of the twelve doors, know the other crew members' responsibilities, because they're yours, too. It sounds matter-of-fact in the manual, the drawings all neat and precise, but planes generally don't crack up so neatly; it'd probably be a shambles.
My mind slides back to a noon takeoff from Paris, headed for New York with a light load of only 177 passengers. We climbed toward the Channel because our route was to go over England and north, out to sea over Northern Ireland. There was a scattering of fluffy cumulus clouds around 5,000 feet, the sky above blue, the Normandy countryside green and lush below.
"Flight eight-oh-three, Paris." It was our company radio calling. The copilot answered.
"Go ahead, Paris -- eight-oh-three."
"Eight-oh-three, we have a telephone [they never say "call"] saying there is a bomb on your flight set to explode at 1340!"
All eyes to the cockpit clocks -- that was about forty-seven minutes from now. Shit!
Scared? No -- because I didn't think it was real. The natural reaction of "This wouldn't happen to me" numbs you unless there's a real accident in progress.
Logic also said that a bomb was unlikely, as most such threats are hoaxes. But we're just off the ground with seven hours ahead of us to New York, and hoax or no hoax you have to play it for real.
A quick return -- Paris air traffic control (ATC) was cooperative when the problem was explained. "You are cleared direct Orly, number one to land." The French grasp situations quickly and act that way, too.
The purser, Buddy Ledger, an efficient old-timer, was called up front: "It's like this," I explained. "We may have to evacuate, so get 'em all ready." Cool as a cucumber, no more excitement or emotion than if I'd simply wanted a cup of fresh coffee.
We started a descent, dumping fuel as we descended, but there wasn't time to get down to landing weight before arriving; as we neared Orly there were just twelve minutes left before the big bang was scheduled, so no time for hanging around the sky. Orly's runway is long, so an overweight landing was less risky than a possible bomb.
I had briefed the passengers during our return, telling them exactly what was going on: "Ladies and gentlemen, this is your captain. We've been notified there is a bomb on board set to go off in forty minutes, so we're returning to Orly. I don't think it's for real, but we cannot take the chance. We should be well on the ground before the time. Please follow the instructions of your purser and cabin team."
That was giving it to them straight. I've always believed in being truthful to passengers about problems. Let 'em have it as it is -- some might faint, but they'll know the score when we revive 'em.
Safely down, and then on the ground we were directed to a deserted area of the airport; they didn't want us to be at the terminal if we blew up.
How do you feel during all this? Annoyed, mostly, still not believing in the bomb, but playing the game. Judgments, actions, compromises all needed because of a phone call.
Out at our lonesome area on the far end of the field -- we were almost out in farm country, the terminal a couple of miles away -- I couldn't see any steps being towed out to us. To play the game right we should get out of the airplane fast: evacuate, slide all the passengers down those long chutes that inflate when the door is opened. That's a regrettable procedure, because someone always gets hurt. I look at the copilot and flight engineer; they're staring at me, expecting a decision. "Let's go!" Action: engine shut down, checklist items all done fast. I flip the switch to ring the bell that will tell the cabin team to start the evacuation, but I didn't want any misunderstandings so I also picked up the intercom. "This is it, evacuate the aircraft!"
"Go!" I said to the two crew members, and they disappeared from the cockpit. I took a minute to double-check that we'd turned all the proper things off, set the brakes, and so on. We'd been thorough, so I was mostly satisfied -- but not completely because in a big complex airplane there's always a feeling that you may have missed something; it's like leaving your house with that question of "What did I forget?" gnawing at your mind.
Last check done to the best of my ability, I rushed out of the cockpit and down the stairs expecting to see a mob of people headed for the doors, but they were already gone, the cabin empty. What a job Buddy and his gals had done. Just to be sure, I ran, circling the length of the cabin to be certain we hadn't missed anyone, and then got to the front door and its chute. Before jumping into it I hesitated a second -- gad, it looked a long way down there; well, it's almost three stories. I jumped, fanny first, feet up, into the chute and slid to the bottom.
The passengers had all been moved away from the airplane and cars and buses were racing out to get them. One man came up to me -- sensitive-looking, with eyeglasses, suit and tie, and a worried look.
"My violin, it is very valuable -- will it be safe? Please take care of it."
"If the airplane doesn't blow up, your violin is safe."
I turned to Buddy and asked, "Anybody hurt?"
"No. One gal, a dead-heading hostess [a flight attendant not working but traveling along to her next destination], turned her ankle. Everybody else okay, including an eighty-two-year-old lady with a cane."
A big sense of relief, because all the people in that airplane are your worry.
We waited a couple of hours and nothing happened. After long discussions among mechanics, airport police, and Lord knows who else, it was decided the airplane was safe. Somehow I was elected to go back on board first.
At the airplane there was a lift with a platform, and I climbed on accompanied by the commandant of the airport police, a proper Frenchman in full uniform topped by his blue kepi -- always neat and impressive. We were raised up to the front door, and in an automatic gesture of politeness I held back for him to go first. Ah, no. He bowed graciously. "Après vous, Capitaine," he said, a hint of amusement in his smile.
We looked around the cabin, toilets, and closets. I searched the overhead racks and found the violin in its case. There were about ten handbags with money and whatever else such bags may hold that the hostesses had left on board; the rule in evacuating is not to worry about belongings, just get yourself off!
I deplaned with ten handbags hanging from my arms and the violin case in hand. The passengers were at the terminal being fed, and when they saw me, the women grabbed the bags for a quick check of their belongings, and the violinist repeatedly bowed and thanked me for his instrument.
Later that night we flew the airplane to New York. You reflect, in the long quiet hours over the sea, how much can be affected by so little: one person -- the authorities concluded later it was an angry employee who'd been fired -- can disrupt so many.
I'm still driving toward JFK, trying to focus on a review of important issues for the flight. The task gets weary and stale; emergency procedures drift out of focus as my mind wanders from airplanes to lighter things: Paris tomorrow, and thoughts of what to do there.
Paris, like any other layover, is a release from responsibility; until the next day I've got nothing to do, nothing to account for except getting to bed for a good rest. I'll have twenty-eight hours to spend in the city I find to be an alluring obsession, one that once you've seen and understood becomes a haven from mundane reality. Experience her with an open mind, and her culture, intellect, beauty, freedom, smells, feeling, and movement will create an almost mystic love. I daydream of an early morning arrival, in the thick mist and cold air that will warm during the day; then the hotel, my room with its brass bed, simple chair, and small marble-topped table of some Louis period, the armoire to store my clothes, a clean bath with the normal fixtures plus a bidet, that civilized apparatus of plumbing and porcelain. The bed has a warm, inviting quilt. From being up all night you will be foggy-tired, relaxed, not concerned about anything in particular and know how good the embrace of that bed will feel.
When people learn that you're an international airline pilot, they often ask how you overcome jet lag. The answer is simple: you don't. No matter how many times you've crossed the sea, jet lag drags on you physically and mentally. You can only get some smarts about it and try to dodge it as much as possible by strategies like napping and thinking ahead to the next period of work and necessary wakefulness.
Sleep will come instantly and the alarm's ring will seem to as well. You've set your clock for 2:00 in the afternoon -- it's essential to carry your own alarm; when you ask for an oddball wake-up in mid-afternoon, 90 percent of the time they simply forget. That's more of the smarts that develop with the job.
It's awful to get up after a three- or four-hour sleep; you feel draggy, with an empty, almost sick feeling inside. Gad, it would be good to roll over and go on sleeping, and it would be so easy to do. But no, get up -- sleep any longer and you won't be able to go to sleep that night.
Because I've lived this Paris routine so often, the daydreaming on the drive to JFK seems real. Get up, shower, shave, dress, and go out. The immediate goal is something to eat, but not too much because dinner is not far away. Down the slope of Rue Balzac for a block to the Champs-Elysées. The afternoon air will be temperate as the sun shines with frail warmth through the fall haze. The street is busy, with cars going by at great speed in a thunder of engines not unlike the start of an auto race; some are trying to find a parking place on the wide sidewalk. People are walking, all kinds of people. Tourists stroll, looking in windows, but the French are in a hurry. Chic ladies dressed as only the French can hurrying to some destination; young people in jeans and sloppy T-shirts -- the world infestation of the jean that homogenizes the young, along with middle-aged folks trying to hold that youth but looking a bit silly; you think of this blue-bottomed army as acting and thinking alike, all with the same values, but that's probably unfair. On Avenue George V, past the Hotels Prince de Galles and George V, fancy cars with chauffeurs wait for fancy people with money. You see them come out: a man in an expensive tailored suit, lovely tie, hair pomaded to slick it down flat and shiny, along with a very fancy blonde with great legs ending in high-heeled shoes, a sexy dress, and makeup to decimal-point perfection. Is she a movie actress or a business girl (to use the French connotation)? Either way, it's amusing.
Then on to a café near the Place de l'Alma; there are chairs and tables outside, a zinc bar inside, the bartender imposing on his elevated floor surrounded by polished machines that make espresso and hot milk. The complexity of the handles, knobs, and dials rivals my 747 instrument panel.
I sit outside. A waiter approaches, small circular tray under his arm, wearing a long white apron and a bored, detached look. I know exactly what I want; I've thought about it since floundering around my hotel room earlier. "Un croque monsieur et un demi-pression, s'il vous plaît" -- a sandwich of thin bread buttered on one side, Gruyère cheese and ham between, well grilled so it comes warm with the butter shining on the outside -- enough fat to jump the cholesterol reading 100 points in a minute, but very good. The pression is draft beer from Alsace, a province along the Rhine that for a period, until the end of World War I, was German, so the beer is good. I suppose some people would be shocked to think of a pilot drinking before a flight, but a beer isn't much drinking and the next flight is about seventeen hours off.
The company rule says no drinking while on a trip at all. Well, I'm not a drinker -- never real booze -- but a beer, or wine, in France? It's ridiculous to think I wouldn't have a glass with a meal.
I think about the one time the wine did get away from me, at a simple dinner with my beloved French friends, Riton and André. Riton was a real old-school Frenchman who knew all the ways of living well -- work was something one did in order to live and not the other way around. He knew every stone and every street in Paris, was an amusing conversationalist, and got serious only rarely, and then generally to express his total dislike for the grand Charles de Gaulle. Riton was one of the best golfers in France and that's how I'd met him many years back, during the more relaxed days of piston airplanes and less frantic schedules when we had two or even three days' layover in Paris.
On the evening in question they took me to dinner knowing I had to get to bed early for a flight to Tel Aviv the next morning. We dined at the Grand Comptoir, an old bistro on the edge of Les Halles market; the food was very good and the wines excellent, chosen from small vineyards the proprietor knew. Riton ordered a Fleurie, a red wine from the Beaujolais region -- my first encounter and, my, it was wonderful and is still one of my favorites. I drank sparingly, knowing I had to fly in the morning. But the conversation was warm and good, and I took little notice that I was drinking more Fleurie than was prudent -- Fleurie is a quaffing wine, not one to sip.
At a good hour we departed and they dropped me off at the hotel. I readied myself for bed and crawled in, stretched out, and closed my eyes. A dizziness instantly overcame me, and my eyes popped open. What's this? I wondered. I closed my eyes again and my head spun with a nausea that said if my eyes stayed closed I'd throw up. My eyes opened again and I stared into the darkness. "My God!" I admonished myself. "You're drunk!" Or at the least I had had too much to drink -- and in just seven hours the phone would ring for crew call. I couldn't possibly fly that soon. This was terrible. I thought it over, made my plan, and picked up the phone to call the airport.
"This is Captain Buck. I'm ill, I'm sure I ate a spoiled mussel [nothing will flatten you more]. I won't be able to take my flight -- have you got someone to cover it for me?"
A pause. "Captain Utgard is set up for eight-oh-one to New York; we can turn him around and send him back to Tel Aviv."
Poor Ed, what a dirty trick I was pulling, but the lie was better than flying "a bit less than efficient," as one old captain put it.
After sleeping until noon the next day I got up well recuperated and flew Ed's 801 to New York in the late afternoon.
Not long after, I saw Ed and apologized for the turnaround I'd caused him and confessed to the real reason. He laughed -- but then he thanked me! He was glad of the extra turnaround, it made it possible to pick up some pay time he'd lost because of a previous cancellation. But it was a strong lesson, and something I never repeated.
My daydreaming stopped and I awakened to the present, to my automobile on the Belt Parkway. I turned off the parkway into JFK airport. The reverie had served its purpose, to put thoughts of home back in storage, where they couldn't distract me from the job or the days ahead. This was not an instinctive process, but one I developed through the years of going and coming as an airline pilot.
You cannot allow the distraction of thoughts of home and family when you're trying to land through low ceiling and fog, or when battling thunderstorms or snow and ice. Nor can you lose sleep or wrap yourself in melancholy over the separation from family thousands of miles away. A more selfish urge is at work here, too: there are the sights and sounds of foreign places to enjoy, and why spoil the experience by mooning about home? But flying off to distant places wasn't a selfish choice. The overseas flights paid best, and since the flights were long, the flying time built up quickly, and that meant more time off between trips -- more time at home. And any hesitation over my enjoyment of the travel was mollified by the thought, "Someday I'll show these places to Jean and the children."
It's a dual life, really, because the airline and its people are a family, too. We were closely knit, knew one another's thoughts, character, and problems. It was an intimate relationship that the family back home wasn't part of.
So pulling open the door to the vestibule that led to the stairs and to the offices on the side of the hangar was also a homecoming. The guard greeted you, other crew members were coming and going, and most you knew and could exchange a quip with by way of hello. You had departed home two hours ago, and here you were, home again -- a different home, but home nevertheless.
As a pilot you don't just get to the airport, climb into an airplane, and go; you sneak up on it in stages. Stage one is a stop at the schedule desk, where a clerk sits behind a counter with a telephone receiver seemingly always glued to one ear, calling to notify crews of future duty, or scrounging up someone to fill in for someone else who called in sick, all the while checking in people like me. When I motion I'm aboard, she checks my name off the crew list, gives me a nod -- and never misses a word to whomever she's talking to on the phone. I lean over the counter for a closer look at my crew list and note that O.B. Smith is tonight's first officer, or copilot, which makes for a warm feeling because O.B. is quiet, efficient, and a pleasure to be with.
A copilot can make a trip or ruin it; get someone who talks too much, gripes about the company, tries to impress you, tells long and boring anecdotes, or is overly aggressive in suggesting ways to run the flight, and the taste is unpleasant. A1 was one of those. He was a captain on domestic, but bid copilot international and the 747 because it paid more and had the romance of flying to Europe and other distant places. But he couldn't stop being captain and started tuning radios and adjusting navigation items without telling me. I finally had to lecture him strongly: "You bid copilot, now damn it, be a copilot and not a co-captain. We'll do things my way, and if you don't like it bid back to domestic." It worked and he settled down, but his resentment always showed.
Now and then there'd be a milquetoast who wouldn't get things done unless you told him each item you wanted. A good copilot is a balance of these things, following, doing as told, but strong enough to point out any error you may have made.
All in all my copilots were fine, like O.B.: a big man from Iowa farm country who came to flying via the navy. (For some reason, naval aviators always seem to come from farms, way out in the middle of the country, far from the sea.) Farm people impress me because they generally have common sense, and if there's one trait a pilot should have in abundance it's good old-fashioned common sense. Farm people also have a way of recognizing that certain things, even unpleasant things, have to be done; they don't bitch about the chore, or cuss out the company because of some obnoxious procedure, and they don't get vocal or outwardly scared when things get tough like the weather going down at your destination when the fuel reserves are low. If that were to happen, O.B. wouldn't change appearance a mite; he'd just settle in to computing fuel, getting weather information, and being generally useful in a matter-of-fact manner. Yes, it's a good feeling to have O.B. in that right seat beside you.
A glance at the rest of the crew: S. C. Bushy, whom everyone just called Bushy, as flight engineer, or second officer; another good man who knows the airplane's innards and workings. The cabin team is twelve hostesses and a flight manager. A few names I recognize at a glance; a couple of attractive gals with a certain verve who'll burst into the cockpit bringing coffee or food and a wise remark, a spark to wake us up for a few moments during the dull grind of a long night.
Then to the mail room and my mailbox crammed with the latest stuff you have to know before a flight.
Paper, lots of it. We're so damn wasteful -- probably one of the worst inventions of all time has been the copier, since it encourages the making and distributing of more copies than are actually needed; computers breed waste, too, as their printers spew long ribbons of paper. For all this paper, the land gets scalped as trees are torn down, and chemicals are dumped into rivers. I've seen the damage from the air, mountainsides made barren, ugly gook flowing out the mouths of rivers and streams into lakes and oceans; acrid smoke that drifts for miles and blots out the sun from a town, city, or countryside. These things can't hide from a pilot's eyes.
I take the papers from my mail folder and lug my black salesmanlike case to a long counter with low stools where pilots sit and bring their operation manuals up to date before flight. The chatter of gossip and tall tales flows from the half-dozen pilots working at the long bench.
The key item in my not-so-briefcase is a beat-up leather-covered six-ring notebook with charts for each airport on route and many off route in case some emergency or bad weather diverts you away from normal routes or places. One packet in the mailbox contains the latest revisions, perhaps a couple of dozen thin paper sheets. There have been changes since you last flew the route and you'd better know about them: a different radio frequency, runway repairs in progress, airport changes; here's one for Geneva, Switzerland -- the airport elevation has been changed from 2,000 feet to 2,014 feet. That's the mark of Swiss precision: someone remeasured it, probably with new instruments. The fourteen-foot change doesn't mean much to me, and I'm certain Geneva's airport hasn't suddenly risen fourteen feet, but it has to be corrected. The old page for Geneva is thrown aside and replaced by the new one.
San Francisco: "I left my heart..." Yes, there's still a part of my heart in San Francisco from my young copilot days. On the San Francisco page, a tower frequency change: the old page is tossed out and the new one put in place. The binders and luggage we carry are big because we carry the information for all the places and routes, from San Francisco to Bombay. It seems silly, and a big burden, but internationally one never knows where the route may be.
Our office was part of the hangar, as many are. They're afterthoughts, stuck onto the side and never well ventilated, and not much light gets into them. The hangar is long, and the offices are located along a corridor that stretches from one end of the building to the other. At the end of the corridor is the entrance to Dispatch and Weather. When you pass through that door you're suddenly in the middle of the action: clerks moving about, writing stuff at their desks, gathering messages, handing them to the dispatcher, who sits in the center of it all worrying about airplanes and flights. The right side area is international; Flight 907 is hung up in Bombay with mechanical problems; Milan is fogged in, what happens to the passengers, mail, and cargo? Concerns like that for every destination from New York to Hong Kong. A partition divides the room and on the left is another dispatcher with a cadre of clerks who handle the North Atlantic; the immediate problems of weather, fuel, loads, and air traffic delays. It's where I do business.
Bill Hussey is on duty, a crisp, pleasant, and sharp individual. We shake hands and pass the pleasantries. "You've got plane 310, it came in on eight-oh-one, no mechanical problems -- you're all set: 395 passengers; Paris looks a little shaky."
Paris is shaky because it may fog in, but that's nothing unexpected; it's fall and not only is Paris shaky, so is all of Northern Europe -- it always is. At this time of year, around October, a high pressure area sits over Europe and gives it those warm hazy days when the light filters through the chestnut trees, creating patterns of soft sunshine and shadow on the ground. But the evening air cools, and as dawn approaches this can form fog -- and our flights arrive in the early morning, around 7:00 A.M. As the day warms the fog burns off: in early October it clears by 8:30 or so; in late October, it may hang on until 9:30 or 10:00, by late November, with the longer and cooler nights, the fog is thicker and it's near noon before it burns off. By December it may not burn off at all. I once spent five days in Paris because no airplanes could get in. They weren't days of complete freedom because you had to be handy in case the fog burned off, but the five days weren't a hardship by any means and, as pilots say in such circumstances, I was there so long I thought of running for mayor. Now it's early November, and the fog situation is chancy. The cure is to take on enough fuel so you can go to the warmer south of France -- Marseilles, for example. But sometimes the payload, or poor winds, make it difficult to put that much fuel on board.
Now over to the meteorologist and his weather map, the man who will tell me what I'll find en route, up in the high sky with its invisible winds that flow from various directions at different speeds and sometimes tumble and churn, creating turbulence. The meteorologist -- we generally call them weathermen -- was Terebelski, a man who'd come to the United States from Poland in some shuffle during World War II that I never dug into deeply enough to learn the details. Terebelski was old-world, his Polish accent still much alive. "Good evenink, Keptain." Medium size, thin gray hair, pleasant smile, and all business -- which he knew very well.
Terebelski's world was up in the troposphere and stratosphere. The troposphere, where we live, is the space where things happen; jet streams move, low and high pressure areas slide over us with their bad weather or good. It's the world of action, that dome of air above us that's about 30,000 feet thick over the poles, 50,000 feet over the equatorial regions. As we take off and climb in the troposphere the temperature decreases, roughly 2°C for every thousand feet we climb. This varies day to day with weather patterns.
Above the troposphere is the stratosphere, which extends up to about 125,000 feet. It's different from the troposphere in that as we climb in the stratosphere the temperature increases with altitude, gets warmer. The air is dry, too, so the weather is clear.
Where the troposphere and stratosphere meet is called the tropopause; in flying talk it's known as "the trop." It really isn't anything except a point of change from troposphere to stratosphere. Often, at the trop, one can see a fine line of dust particles, stuff from where we live down below that can't go any higher because the warmer stratosphere prevents its climb, just like the pollution in Los Angeles stays there because of an inversion -- warmer aloft, like the stratosphere.
What does all this mean to me in a jet airplane? Well, I want to get as high as possible because up high, simply put, we get more miles per gallon. The catch is temperature; if the airplane is heavy, the altitude it can climb to is limited by temperature. If it's too warm for the airplane's weight, performance deteriorates, because warm air is thinner, so it has fewer mole