There are two sets of Aerial Challenges to complete in GTA 5: Knife Flights and Under the Bridge. Completing both of these will reward you will the Close Shave trophy or achievement. For the Knife Flights, you must fly between two buildings with the plane on its side. This can take a little while to master, but once you get the hang of it you'll finish all 15 in no time.

Use the Stunt Plane for most challenges as it's easy to steer, whereas the jet has very high sensitivity steering. I used the jet for all the knife flights as it keeps its speed well so it doesn't lose much altitude when performing the knife flight.

There are a total of 50 bridges in the game that you need to fly under. A helicopter makes these Missions easier. Pass completely under the bridge without touching the floor below, you cannot touch ANYTHING while going underneath it. The easiest helicopter to do this with is the Buzzard Attack Helicopter.