Flight allows the user to levitate and fly at high speeds.
Christopher's Quirk covers himself and whatever he is in contact with inside an aerodynamic barrier that protects from heat, cold, and physical harm. He can control how much of what or whom the barrier protects.
Due to the immense strength Christopher possesses, including being able to carry a giant ship or even the Tokyo Sky Egg, it is presumed this aerodynamic barrier grants him said superhuman strength, alongside his flying abilities.
The Bombers' version of this Quirk simply gives the creatures wings to allow for flight.
The main weakness of Christopher's Flight Quirk is that the more he spreads his Quirk around someone and/or something else, the less protection he has around himself.