How to increase land check radius?

So every flyer does a land check to verify where to land, if they are pretty high up they wont receive this value and will stay up flying in the air. I was wodnering if there is a way to increase the size of the land check. so that they will know to land from so high up in the air, Im pretty sure it has to do something with the ai as I checked with acceptable landing radius and he landed in mid air and that pretty much is something we dont want so.