As a physician who travels quite a lot, I spend a lot of time on planes listening for that dreaded “Is there a doctor on board?” announcement. I’ve been ( 1) only once — for a woman who had merely fainted. But the accident made me quite curious about how ( 2) this kind of thing happens. I wondered what I would do if ( 3) with a real midair medical emergency — without access to a hospital staff and the usual emergency equipment. So ( 4) the New England Journal of Medicine last week published a study about in-flight medical events, I read it ( 5) interest. The study estimated that there is an average of 30 in-flight medical emergencies on U. S. flights every day. Most of them are not ( 6) ; fainting and dizziness are the most frequent complaints. But 13% of them are serious enough to ( 7) a pilot to change course. The most common of the serious emergencies include heart trouble, strokes, and difficulty in breathing. Let’s face it: plane rides are ( 8) . For starters, cabin pressures at high altitudes are set at roughly what they would be if you lived at 5,000 to 8,000 feet above sea level. Most people can tolerate these pressures pretty easily, but passengers with heart disease ( 9) experience chest pains as a result of the reduced amount of oxygen flowing through their blood. Another common in-flight problem is the so-called economy class syndrome. ( 10) happens, don’t panic. Things are getting better on the in-flight-emergency front. Thanks to more recent legislation, flights with at least one attendant are starting to install emergency medical kits to treat heart attacks.