Ask the pilot

Recently while high over the Atlantic in a 747 we heard a very loud bang, followed by a palpable vibration through the cabin. The captain informed us we'd suffered an "engine pop." A what?

Engine pop. Ugh. Pilots, in their attempts to put people at ease, can often oversimplify things to the point where people giggle at them. What he was talking about was a "compressor stall," a phenomenon where the airflow through a turbine (jet) engine is temporarily disrupted for one of a few possible reasons. It's not a big deal. It can damage an engine, but usually it doesn't.

As a nervous traveler I am constantly trying to read the facial expressions of the cabin crew. If there were a true emergency on board, is it general policy to not inform passengers in order to avoid panic?

Many people expect nothing less than compulsive deception at the hands of the airlines, but no, there is no official concealment policy. The carriers themselves have bred much of this culture (see above), but while they could do better in the articulation department, they do not, as a rule, intentionally mislead passengers or withhold information during in-flight emergencies.

That said, a crew will not, generally, inform passengers of more commonplace problems or malfunctions with no real bearing on safety: "Ladies and gentlemen this is the captain speaking ... Just to let you know, we've received a failure indication for the backup loop of the secondary smoke detection system in the aft cargo compartment." Being blunt about every little problem invites trouble. In the above example, passengers arrive home with stories like, "Oh my god, the plane was on fire." Which isn't to say people aren't bright enough to figure out what is or isn't a dangerous situation, but often you're dealing with jargon and terminology that lends itself to exaggeration and misunderstanding.

Could you clear up my lingering doubts and suspicion concerning TWA Flight 800. I watched a newscaster express his intense skepticism that a 747 would blow up in mid-flight due to a mechanical problem. What do you think happened to Flight 800?

There has been an almost pathological refusal by many people to believe mechanical failure caused the explosion of the Boeing 747, which blew up near Long Island in the summer of 1996 on its way to Paris. But in my opinion that's probably what happened. The airplane, an old 747-100, had been baking on a hot JFK tarmac up until departure, superheating the vapors in its empty center fuel cell (a 747 does not need a full complement of fuel to cross the Atlantic). There have been at least two other cases of exploding fuel tanks on planes that languished in the heat. One of these was a Thai Airways 737 that exploded at the gate in Bangkok, killing a flight attendant.

" ... intense skepticism that a 747 would blow up in mid-flight due to a mechanical problem." Indeed, it's not very likely. But neither is it impossible, and catastrophic mid-flight failures have occurred several times in the annals of commercial aviation.

What was it like, from a pilot's point of view, on the morning of Sept. 11? What were your thoughts and impressions?

Portions of this answer were originally published in "Back in the Saddle."

I watched the events unfold with a kind of horror and morbid fascination. And after my immediate, reflexive shock, I started to sink into despair over how, I suspected, those of us in the airline business were going to suffer.

I was flying from Boston that morning -- deadheading to work as a passenger -- as were both of the World Trade Center aircraft. I watched American Flight 11 take off. Our plane departed just after it, on Runway 9, and I passed directly over Manhattan just a few minutes before the attacks. Because of a "security issue," our captain told us about halfway through the flight, we would be diverting. Pilots love to dish out semi-comforting euphemisms, and this little gem would, in time, be one of the more laughable understatements I shall ever hear a comrade utter. It wasn't until I joined a large crowd of passengers in a concourse restaurant that I learned what was going on.

The most vivid impression was the video of the second 767 hitting the building -- the one shot from the ground in a kind of 21st century Zapruder film. The picture swings left, picks up the United jet, its gray-painted fuselage and tail logo clearly visible, moving swiftly. Very swiftly, in fact. My trained eye notices the plane is traveling at a much higher velocity than it would be normally at such a low altitude. The plane rocks slightly, picks up its nose, and like a charging, pissed-off bull making a run for an unfortunate matador, it drives itself, accurately, into the very center of that building. The airplane simply vanishes. For a fraction of a second there is no falling debris, no smoke, no fire, no movement. It's as though the plane has been swallowed by a skyscraper of liquid. Then, from within, you see the white-hot explosion and violent, spewing expulsion of fire and matter.

To me, had the airplanes crashed, blown up, and reduced the upper floors of those buildings to burned-out hulks, the whole event would nonetheless have clung to the realm of believability. But it was the groaning implosion, the buildings dropping and the white clouds of wreckage funneling like a pyroclastic tornado through the streets of lower Manhattan, that catapulted the event to one of pure, historical infamy. They fell down. The sight of those ugly towers collapsing onto themselves is the most sublimely terrifying thing I have ever seen in my life.

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