Against C3, going ground is better. There is about half the number of defending helicopter wings as interceptor wings, and you have the time to maneuver freely.
I'd recommend these units:
One with 1000 OAAMB + 600 MRMB (best to buy max Q and upgrade as you're able)
Use this to attack defenses on an ungarrisoned target (Town/County) and do so until no helicopters respond, this will clear out all air defense you need to worry about. The MRMB will absorb damage and the OAAMB will be freely destroying Helicopters. If you get it in the country, it can attack any location.
After this, it would be wise to attack each helicopter wing directly to prevent them from being resupplied. C3s will usually resupply 100 helicopters in one of the units after several minutes. Wiser to bypass this.
One with 1600 MRMB (best to buy max Q and upgrade as you're able)
Use this to clear out garrisons on an
Nice post Mizore. I took something from it myself. I've been using 1000 MRB's and 600 AAMB's.