The first step to completing this is to unlock the Wingsuit
perk. Now, I would recommend going to a helicopter or plane shop, and taking it to highest peak of the map, on the west side mountains between Holland Valley and Whitetail Mountains. Upon landing, you should be able to just jump off the side of the cliff, press
to engage the wingsuit, and level out so you can fly as far as possible. From this location, you should be able to easily grab 2,500m+ on each jump. Your progress is tracked until the challenges menu as well. Repeat this process until it unlocks.