There's 2 possibilities Easy
Ok
a) you have the airfields from the same country and kill shooter off (so you can furball)
Then use PROTECTOBJECT variable in the arena settings GUI and set it to 1 -> this will prevent that you damage friendly objects
b) Different countries:
There's no possibility to PROTECT enemy structures but you can set the DOWNTIME MULTIPLIER variable (also in the arena settings GUI) to 0 that should result in instant resurrection of a destroyed building/object.
Hope that helps.
DW6