An AED can be used by someone without formal medical training because the device determines the heart rhythm and whether it likely can be corrected by electric shock. If so, it automatically delivers the shock. In such cases, response time is critical. Medical training of cabin crews varies, but usually includes basic cardiopulmonary resuscitation and AED instruction. If you have certain health conditions, some airlines require a medical certificate verifying that you're medically stable enough for air travel.
Airlines based in other countries have different regulations.
Currently there are no universal guidelines for handling in-flight medical emergencies. Women are usually advised not to fly within 5 to 6 weeks of their due date. Intense pain that can occur during a plane's ascent or descent is due to unequal pressure between the middle ear chamber and the cabin environment. Chewing gum, drinking liquids, yawning and repeated swallowing may help relieve the pain. Try not to sleep during descent.