unfortunately without mods, it cannot be unlocked :L
Sadly, there is not a jetpack in Halo 3: ODST. However, in Halo: Reach, the jetpack is a versatile and readily available armor ability.
You can't drive a pelican in Halo 3.
you cant
press x
U Cant
in halo 3 there is none to drive
you cant
to stay on a pelican i keep on pressing x, but to jump on it, i have no idea
pp
Sorry but you can't fly one.
No there is not a mod
Unlock what head?
A Hawk is not from Halo 3 it is from the game Halo Wars which is not associated with Bungie. Halo Wars Ensemble Studios created the Hawk. You may be thinking of the Hornet or Pelican.