From Halopedia, the Halo wiki
Flyin' High is a medal in Halo 4 and Halo 5: Guardians. It is earned by achieving a massive Mongoose or Warthog jump with a passenger. It awards you 5 points.
An easy way to obtain the "Flyin' High" medal is to drive a Mongoose with a passenger off one of the tower's launch pads in Ragnarok.
The Halo 4 version.