Look involves a field of vision That's directional and distance related. If you are looking at something close the distant things will be out of focus.( Depth of field) If you focus for something at say 200 yards the difference between that and infinity is not much whereas from say 2 feet to 300 feet is a lot. An object approaching near directly at you at High speed is NOT hard to see because in it's frame of reference It's not moving fast at all and may appear almost stationary. Fog or dust can be a factor at longer distances or even with Heat Haze which distorts the atmosphere by refractive index changes with air density. If you can't be sure don't just say "She will be right" Wait till you can be sure. When you have 2 Jets approaching each other the speed involved is faster than a bullet, so you have very little time to react. IF you had a motorcycle on final at 108Knots in decent visibility you SHOULD be able to see it, if you are at the threshold waiting and looking as you should be doing if a vehicle may be likely to come down the road, on your right. Nev