While I agree with your logic that I shouldn't be too concerned with catching something from some infected guy ten rows behind me, you skim over the fact that people are packed into the cabin almost cheek-to-cheek. I'm REALLY concerned about the people next to me, behind me, and in front of me. If I'm unfortunate enough to be in the center seat, then there are eight mucus factories within three feet of my head, and if any of them have the flu then I've got an undeniably higher chance of getting sick.

I understand that you have travelled a lot, but being a pilot I assume that you are not always packed into the cattle car with the majority of the passengers. You're lucky.

Patrick,

Please, help me out on this: I'm typed as a pilot on the MD-11, B-737, L-382, and SA-227, and have "plumbed" the DC-10 and the B-727; also flown a variety of military jets. I'll be the first to admit I'm no systems guru, but I swear I've never flown an airplane that filters and recirculates air. My understanding has always been that it enters via the compressors, passes through the packs, flows through the cabin and lower cargo holds, and then exits via the outflow valve.

I'm not saying that there aren't airplanes that DO recycle air, I'm just saying that I don't think that any jet from MY generation does. Please help me get up to speed if I'm wrong.

BBH

Thank you for that touch of sanity in media. With all the breathless headlines and "breaking-news-itis" that's infected CNN and others the past few weeks, may your article be one of the ones that finally puts the swine flu (or H1N1 or whatever) story to rest.

Patrick, the odds are that you didn't catch anything on that plane, as the incubation time would be way too short. More likely, you were already infected with a particularly-bad cold or flu when you got on that plane, and the symptoms just happened to materialize in-flight, possibly hastened along by the physical stress of traveling. I had a similar experience just before Thanksgiving 1976, when I became horribly ill with fever, chills, muscle aches, and lots of other unpleasant symptoms on an Amtrak run between NYC and Boston. Did I catch the bug during the four hours spent on the train? Almost certainly not; the symptoms just happened to hit during those four hours. You probably didn't get your illness on that DC-10, either, but just had the bad luck to have it start to affect you while you were on board.

I'd echo what Mr Smith said in his letter. The air may be changed frequently but you could be jammed in that plane in close proximity to hundreds of coughing and sneezing people for hours on end. As a pilot you're just not exposed to that (although I guess the cabin crew are).

Planes can be an international clearing house for germs. It seems to me that somebody from the other side of the world could be spreading germs that are uncommon in your neck of the woods and to which you might therefore have little resistance.

Boeing says that between 94 and 99.9 percent of airborne microbes are captured, and there's a total changeover of air every two or three minutes.

While the first part may well be true when the air enters the plane cabin, the "two or three minutes" changeover is completely disingenuous. Processing fresh air costs fuel. There are plenty of airlines that minimise the amount of changeovers they do in order to save fuel, sometimes only as often as a few times a half hour.

So while I agree that planes are not as grubby in terms of air as people sometimes assume, they're generally not as pristine as Boeing is trying to make out.

Processing fresh air costs fuel.

Oh really? How do you figure that? When the engine is on, the compressors are on. In fact, they _must_ be on.

There are plenty of airlines that minimise the amount of changeovers they do in order to save fuel, sometimes only as often as a few times a half hour.

Do you have even a shred of evidence to support this outrageous claim? Evidence that doesn't come from, say, Diane Fairechild, the ex-flight-attendant with her sensationalist but mostly fact-free books to sell?

If you have some, please post it and I'll eat my words. But until then, as Patrick stated: the "turn down the air quality" meme is the myth that just won't die.

On the other hand, there are numerous scientific studies you can google up that show that the air quality on your average airline is worst when the doors are open on the ground. As it obviously should be if you think about it for just a second.

Internal air systems on big jets do have "hi flow" and "regular flow" settings -- the high used in particularly hot or cold climates when the jet is taxiing on the ground. But this does NOT mean the air quality changes significantly when the system is switched to "regular flow" after the heat/cold of the ground has been cycled out sometime after takeoff.

Yes, it has already happened. As you can see from the articles, it's not entirely clear if the infected mosquito was on the plane and then infected a person who in turn infected mosquitos which then infected these 2 patients. More likely, there was an infected person on the plane who then infected the mosquitos which then transmitted the malaria parasite.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1169563

http://www.medscape.com/viewarticle/444046_print

I

Mr. Smith correctly points out that that dry air in airplanes will tend to dry out bacteria and molds, and reduce the likelihood of catching bacterial infections, not to mention reduce the likelihood of having mold colonies producing toxins. But viruses aren't bacteria, and the flu viruses actually prefer cold, dry air, which is why the seasonal flu is in the winter, not the summer. So for the transmission of flu, the interior of an airplane is pretty great. Cool, very dry, with lots of people crammed together. Yes, you're not likely to get the virus from someone 12 rows up sneezing, because the droplets won't make it to you. But if you touch something they've recently touched, like an armrest, or the bathroom door, you very likely could catch their virus.