Smart HQ attackers leave some of their cap over the HQ, because C47's are easy kills, M8's too...
I have seen that more than one time, effectively changing that resupply 20 minutes to approx one hour.
First wave of C47 where shot down by some P51's, climbing to 15k mustangs took time, first not finding them without radar/radar bar, chasing them away took more time, by then the HQ re-upped by itself, no-one wanted to fly the C47 as long as the strat's flashed.
Many Rooks logged even before enemy fighter cap where gone, trying to find fights in a 25*25 mile sector with a flashing field, maybe lucky meeting 1 or unlucky meeting 25 enemies, not knowing if friendlies / squaddies are close or not.
Finding the fight is what this game is all about.
When we lose HQ (something that is entirely preventable). I land and up goons to resupply the HQ. HQ raiders are easily spotted and tracked by the darbar.