A medical emergency occurs in the skies about once every 600 flights, according to a study that appeared in the New England Journal of Medicine.
The most common maladies are fainting, respiratory problems, heart trouble, and nausea or vomiting.
The study found that it's rare for an in-flight emergency to end in death, but the worst outcome does take place 0.3% of the time.
What happens next?
Despite what you may have heard, crew members do not stash the body in the lavatory (that sounds like a tasteless joke that too many people took seriously) and pilots do not automatically have to make an emergency landing.
Surprisingly, the Federal Aviation Administration (FAA), the U.S. government agency that regulates safety in air travel, doesn't offer much guidance when it comes to in-flight medical deaths (apart from mandates to report the incident properly).
FAA regulations require aircraft to be outfitted with emergency medical equipment kits (including an automated external defibrillator) and require flight attendants to undergo training (including CPR) for medical emergencies, but airlines mostly make their own rules for handling things when the kits and the training don't prevent a death.
Fortunately, carriers have come up with protocols that adhere to nonbinding guidelines devised by the International Air Transport Association (IATA), an industry group representing the world's aviation companies.
IATA recommends that flight crew members continue attempting CPR on the passenger in extremis for at least 30 minutes unless breathing and a heartbeat resume or conditions on the flight become unsafe due to turbulence or other obstacles.
During the emergency, crew members will also request the assistance of any doctors on board the plane. As Condé Nast Traveler points out, this isn't just to have the help of a pro but also because only a physician can legally declare someone dead.
If there aren't any doctors in the cabin, an unconscious, unbreathing, unresponsive passenger is only presumed dead.
Flight crews will notify the cockpit immediately during an onboard emergency so that the captain can get in touch with one of the organizations that offer medical assistance via audio communication from the ground. MedAire's MedLink service has doctors on call to offer this type of support; Delta Air Lines uses a nonprofit called STAT-MD.
These ground-based doctors will advise the pilot on whether an emergency landing might help the person having the medical issue.
In the event of a passenger death (whether presumed or physician-verified), notifying the cockpit will again be flight attendants' top priority so that the captain can alert the destination airport and prepare the proper authorities to meet the flight upon landing.
An emergency landing is not required. In fact, it's highly likely that the flight crew, onboard physician (if present), and remote medical advisors will determine there's no point in landing or diverting the plane from its original course if a passenger is dead. After all, how would that help?
The next task, then, becomes taking care of the body for the remainder of the flight (as if flight attendants' jobs weren't tough enough already).
IATA recommends moving the body to a seat with "few other passengers nearby," such as in business class or a row with empty seats.
That's not possible on a full flight, however, so IATA says crew members should "put the [dead] person back into his/her own seat" in an upright position, using the seatbelt or other restraining equipment to hold the body in place.
"Close the eyes, and cover the body with a blanket up to the neck," IATA advises, "if a body bag is not available."
Once the plane lands, the body and anyone traveling with the deceased should stay where they are while the other passengers disembark. At that point, medical professionals and airport authorities take over.
As in any end-of-life situation, preserving dignity and exercising compassion should take precedence above all else.