User blog comment:DeadpoolN7/Why didn't the Alliance try this earlier?/@comment-4721065-20130527083419

Basically what Temporaryeditor has said. However, props for the example from Starship Troopers. Technically, the non-involvement of airforce in the final battle of that movie was also justified, as it was always meant to capture a specific Arachnid, rather than to simply eradicate everything.

As for other engagements, heavy presence of those plasma AA bugs off-screen could have been the reason, but unfortunately we aren't given enough evidence to believe that. This, and many other idiot balls really hurt the movie since unlike other blockbusters SST actually does a message and a theme, so you need to keep your brain engaged, but at the cost of being unable to take anything seriously. I almost prefer the sequel, since it was far more grounded, believable and thematically consistent, though that was offset by its $7m budget and lessened characterisation.

Both movies (haven't seen Marauder yet, so can't speak for its quality) absolutely trounce the last year CGI crapfest known as Starship Troopers: Invasion, however.