I'd bet that the jets looked like they were going slow due to how the terrain is rendered at that height as well as the fact that we see the pace of soldiers running during the chopper scene and not during the jets.
What I mean is, during the chopper scene, you can see soldiers running and they look slow compared to the chopper. In one of the jet scenes in the bottom right (I think?) you can see a vehicle of some sort that resembles a chopper that is moving seemingly slow compared to the 4 jets in the air.
All this being said, anyone hoping to see a VTOL jet or some sort.