+1, but there is a way around that. Attack from above, not the horizontal.
It is not always necessarily the case. I hardly use a tank, however I am able to track and kill bombers fairly easily (however I cannot hit a thing with an osti?!?!)
Fighters I can hit in the manner you described.
I have been killed 3k-4k away from a panzer flying at 4,000ft, when I was not even attacking it. Some players are especially good at using tanks as AA.