By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) – Have you ever wondered about medical emergencies occurring on flights? Probably not, but as a physician it always crosses my mind because you just never know.

Last week there was a report in the New England Journal of Medicine which found for every 604 flights, there’s 1 in-flight medical emergency. The scientists looked at five commercial airlines and reviewed almost 12,000 flights.

Just in case you are wondering, the most common medical problems were fainting or near fainting, breathing problems, and nausea/vomiting. Seven percent of flights on which there was an emergency had to undergo an emergency landing.

By the way as far as helping out on a plane with a medical emergency, there is no legal obligation to intervene, but health care providers have a moral and professional obligation to act as good samaritans, and are covered by the 1998 aviation medical assistance act, which includes a good samaritan provision.