You can unlock items if you do the following:
Jas39A: Finish sub-mission 4 in area 5.
F/A-18 Hornet: Complete sub-mission 7 in area 2.
F-35B: Complete Sub-mission 7 in Area 7.
F-22A: Complete Sub-mission 10 in Area 7.
F-16AM: Complete Sub-mission 6 in Area 5.
F-15E: Complete tactical mission 1 in area 6.
F-15C Fighter: Finish the sub-mission 5 in area 4.
F-117A: Complete tactical mission 1 in area 4.
F-16C: Beat sub-mission 4 in area 2.