I am watching Chronicle (2012) and this question just popped into my mind. What techniques are used for filming flying human scenes? Do they always use chroma keying or are there other techniques?
The primary technique used for flying stunts are wire harnesses and then wire removal. The actors wear a harness which is connected to wires that suspend the actor in mid-air. If the scene is filmed in front of a green screen (chroma keying), then the wires can be removed automatically in most cases, before the background is added. If no chroma keying is used, as in the scene below, then an editor must remove the wires from each frame manually.
Most of it are done with chroma keying. Sometimes with something like a blower blowing air against the actor to stimulate the effect of moving through air. Then composited against a background.