If someone passed out on a plane, how would i be able to help them?

Difficult: There's little you can do. Try to check their pulse. If it's weak (low blood pressure), have them drink water if able. Place them in a head down, feet up (trendelburg) position. If their hr is very fast (>150), you can try carotid massage if you know how. If they awaken short of breath, most airlines have oxygen. In a real emergency, the pilot must divert to the nearest airport.