At any given time, about one million people are up in the air aboard commercial flights. And so, it’s expected that the occasional medical event will occur on an airplane. Luckily these incidents are uncommon; about 1 in 604 flights host a medical emergency, according to the Journal of the American Medical Association. But do some factors put certain people at risk, more so than others? And how are medical emergencies handled safely at 32,000 feet elevation?

Yes, in rare cases the environment of a plane can exacerbate certain health issues. Because planes are pressurized, and the environment mimics that of about 5,000 to 8,000 feet in elevation, oxygen levels are a bit lower than you normally see on ground (unless you’re a mountain dweller).

For the most part, this situation only causes mild symptoms for a few people, such as gastrointestinal trouble, wooziness, and fainting. But in rare situations, the lower oxygen levels can stress existing respiratory and cardiovascular issues.

Of course, airlines sometimes just happen to be the location of events that were going to occur anyway, like strokes and heart attacks. And in recent years, events linked to mental illness or drug overdose have also become more common on board planes.

All employees on board commercial planes are taught basic first aid skills, such as administering CPR and supplementary oxygen. When more serious medical events occur, the pilot or an attendant will often make an announcement, inquiring whether anyone on board has medical training and is willing to help. During extreme emergencies, pilots will sometimes decide to divert the plane and land at the first available airport.

Luckily, deaths on board an airplane are extremely rare, with only 1 in 8 million travelers passing away while flying.

If you’re worried about the health effects of flying, consult with your doctor. In most cases you will be cleared to travel, but if you have COPD, severe anemia or cardiovascular or respiratory diseases, the lower oxygen levels could be stressful for you. And if you’re at high risk of blood clots, remember to get up and move around frequently.

If you plan to travel to a foreign country, consider the impact of emergency medical bills. Talk to us, licensed agents about a Medigap policy and how it can help with unexpected expenses outside the geographic range of Medicare coverage.