Unlock the following Elite armor permutations by fulfilling the requirement listed.

Ascetic (Body): Get the Up Close and Personal Achievement
Ascetic (Head): Get the Steppin' Razor Achievement
Ascetic (Shoulders): Get the Overkill Achievement
Commando (Body): Get the Triple Kill Achievement
Commando (Head): Get the Overkill Achievement
Commando (Shoulders): Get the Killing Frenzy Achivement
Flight (Body): Complete Tsavo Highway (on Heroic or Legendary)
Flight (Head): Complete the campaign mode (on Legendary or Heroic)
Flight (Shoulders): Complete The Ark (on Heroic or Legendary)