This game is one of my all time favorites. A relatively simple game, but I love the building, expanding and resource gathering/control. A favorite for a lighter game that sill has plenty of fun and replayability to it.
One of my tactics for taking out tough AI defense strong points or opening gaps, was to use air transports to move in missile crawlers or other long range units just outside of air defense range. Of course, that varies since the AI seems to build a lot of missile crawlers or missile defenses with long range. What I would do in tough fighting is air transport units forward to attack, then transport them back again the same turn to avoid counter attack. To cover longer distances plus the pull back, I'd keep air transports staged along the way, covered by mobile anti-air (transported in) and fighters. That could be risky though, if the AI mass attacks with fighters, but otherwise it could really work well. Sometimes though I don't use that tactic since it seems to give me too much advantage.