PHOENIX - "We are projecting that 43 million Americans are going to be traveling this holiday season," Tamra Johnson of AAA said.

A record number of Americans are getting ready to take off for the holiday weekend.

But once you get on board, then what?

With nearly 50 in-flight medical emergencies happeneing per day in the US alone, the dangers don't stop once you're wheels up.

In three out of four emergencies, trained health professionals aboard the plane came forward to help. Doctors helped in nearly half of cases, and nurses provided care in 20 percent of emergencies.

And luckily, Phoenix has one of two centers in the entire country where emergency physicians on the ground advise flight crews on what to do.

When most people get on a plane, they probably don't think, "What do I do if there's a medical emergency?" But it happens, and when it does, airlines around the world call Phoenix for help.

MedAire is who you get on the other end of the lifeline when you're on a plane, thousands of feet in the sky and something goes wrong.

The Medaire call center is located at Banner University Medical Center Phoenix. A communication specialist takes the call, then hands it to a physician.

More than 120 airlines around the world rely on experts in Phoenix -- doctors available around the clock to walk them through What to do.

Dr. Lester Tukan spoke about some of the issues they are confronted with, "Fainting is very common, chest pains -- all sorts of things ... cardiac arrest."

Flight attendants have basic training but even with medical supplies on board, only a trained medic can use them.

Also, when you're up In the air, there's an added risk.

"Even if you're at altitude over the mainland, it could take you 30 minutes to get down to the ground," Tukan said.

Doctors can suggest diverting the plane but, ultimately, it's the captain's call.