I know this is a while ago but I figured if I found this looking for a solution for my needs others will also. My flight game is a bird not a jet, but with a bit of stretching your gameplay mechanics a bit I bet you could find a reason to make this work for just about anything.
So right, here’s what I’m doing. First off the higher my bird flies the more stamina it takes to go higher, this makes it more efficient for the player to hug the ground. (I have some stylized Niagara wind lines that make this intuitive for the player) I put exponential height fog pretty strong and have four collision volumes near but not on the map edges. When the player runs into it scales up an MPC scalar that in the level blueprint (on tick, yes I know) scales up the fog. When the fog value is maxed they teleport the player to the opposite edge of the map with their same rotation and trajectory (just move the X or Y and keep the rest the same) then scale the fog back down. This way you don’t get too high to see the edge coming up, when you hit it you fog out and when you fog back down you’re flying back into the same map with controls intact. I’m hoping to get away with a 2.6 km landscape. Pro-tip though whatever landscape you use make sure the edges line up. I am going to go back to step one and make my heightmap texture tileable so that my z gets preserved otherwise I have to have an altitude jump so there’s no one to accidentally clip yourself under the map.