I forgot why I named the game X. Maybe because you play a Taxi driver? The readme.txt included has this:
\ / \ / \/ /\ / \ / \ (insert name here) Ludumdare 2010 entry by Allefant Controls: Cursor keys or ASDW: control rudder Page up/down keys or RF: control throttle Click mouse to turn camera. When you see a yellow person with a triangle above there had, fly close to them but make sure you stay above them. They will hop on. Fly them to the triangle of the same color and they will hop off.
And a video: