User blog comment:Demons of Hræsvelgr/I need help with Joint Assault./@comment-4503347-20130309184809

Hey man, this may come a bit late, but I found the necessary info from a Japanese site that will help you:

YR-302 Fregata - Complete Mission 14 (Dragon Lair) in ACE difficulty or complete Mission 13&14 (Dragon Killer)

XR-45 Cariburn - Complete Mission 12 (Nightwatch) in ACE difficulty or complete Mission 03&04 (Red and Black) in ACE difficulty

XFA-27 - Complete Mission 19 (Desert Dust) in ACE difficulty

X-02 Wyvern - Complete Mission SP 1 (Operation X)

ADF-01 Falken - Complete Mission SP 2 (Ace of Aces)

Fenrir - Complete Mission 21A (Reprisal) in ACE difficulty

GAF-1 Varcolac - Complete Mission 21A (Reprisal) in ACE difficulty with an S rank

Hope that helps!