I have to say that I never bought into the concept that soldiers would transition back and forth from fighter pilots to grunts. Pilots are simply too well trained to be expended as grunts. It never could happen. If they had split the character focus from a group of grunts to a group of pilots, it would have worked so much better. Kinda like in Starship troopers, a group of soldiers and a group of pilots. All in combat against the same enemy but different stories because of different roles.
And as an aerospace engineer, the "Hammerhead" was always a lame looking endo-exoatmospheric concept to me. Never liked is at all.
Paul