Acks, fuel, ammo dumps, hangars, radar. Don't have to destroy them in a particular order but I can recommend taking out the vehicle hangar first, to avoid the spawning of Ostwinds From Hell, and then ack, radar and hangars. Or, if you're part of a strike force, hangars, radar, ack
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The installations you see are start targets, such as training facilities, oil refineries etc. If they're near your territory, theiy're friendlies and your ammo won't do any damage
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Baron Claus "StSanta" Von Ribbentroppen
9./JG 54 "Grünherz"
"If you're not living on the edge, you're taking up space"