I think the conflation of UFO = Aliens doesn't help the topic very much. UFO means exactly that, it's a flying object and we don't know what it is, thats all. If we're saying it's an Alien then, by definition, we're saying we know what it is, so it can't be an "Unidentified" Flying Object.
Two points here -
1. 20,000ft sounds a lot but it's only 3.7 miles - You can tell what a articulated truck and trailer looks like at that distance no problem as you can distinguish a 6ft Human at 2 miles (
link).
2. Miltary pilots have virtually perfect vision (to become a Pilot initially) and more importantly they're trained to ID objects from the air. Most recently in Iraq/Afghanistan/Syria they use their eye unaided by optics to identify objects like enemy trucks, pick-ups, huts etc visually first so they know where to aim their targetting pods towards allowing them to use the pods more accurate "zoomed in" image for accuracy.