Well, IMHO planes in SH5 do not act so aggressive as you would see it in SH3, at least that's my experience when playing the early war 1940-1941, I have recently been overflown without the plane dropping any bomb, he must have been on exercice only or without ammo..
But make use of the radio man's 'Signal Contacts' ('Kontakte melden'), and if german airports are close you will get *great* assistance by friendly planes comming in against your naval targets, and this time my friend: they will do the whole job, not leaving anything for me left
And no, for that you won't receive any credits or points...but that's ok I think...