Two rules to remember and you'll always land:
1. ALWAYS "land" on concrete. Wether it be on a veh base, air base, or town. Make sure you are on concrete and you will always make it, even when damaged.
2. If the base you are at is not flashing, which includes the town at an airbase (it can flash alone if being attacked by a gv), you can "land" anywhere. But make sure it isnt flashing.
On a side note, if you spawn into enemy territory and there are no enemies within X distance of you and you are on or still within X distance of the spawn point... you can "land" there as well. X = ? distance. I do not know the distances of approximation to enemy gv's on order to be safe or not.
Hope this helps.