AE.9
Spanish designation of the Northrop F-5B.
F-5-21
Temporary designation given to the YF-5B.
YF-5B
One F-5B was fitted with a 5,000 lbf (2,268 kgf) General Electric J85-GE-21 engine, and used as a prototype for the F-5E Tiger II.

F-5B
Two-seat trainer version.

F-5B(G)
Two-seat trainer version of the F-5B for the Royal Norwegian Air Force.

F-5BM
Two-seat trainer version in use by the Spanish Air Force for air combat training.

F-5D
Unbuilt trainer version.

F-5F Tiger II
Two-seat trainer version of F-5E Tiger II, AN/APQ-167 radar tested, intended to replace AN/APQ-157, but not carried out.

F-5F Tiger III
Upgraded trainer version of the F-5F in use by the Chilean Air Force.

F-5T
Upgraded F-5F in use by the Republic of Singapore Air Force.

F-5THF (บ.ข.18 ค)
Twin-seat version of F-5TH currently in active services with the Royal Thai Air Force as of May 2020.

F-5FM
Upgraded trainer version of the F-5F for the Brazilian Air Force.
AE.9
Spanish designation of the Northrop F-5B.
F-5-21
Temporary designation given to the YF-5B.
YF-5B
One F-5B was fitted with a 5,000 lbf (2,268 kgf) General Electric J85-GE-21 engine, and used as a prototype for the F-5E Tiger II.
F-5B
Two-seat trainer version.
F-5B(G)
Two-seat trainer version of the F-5B for the Royal Norwegian Air Force.
F-5BM
Two-seat trainer version in use by the Spanish Air Force for air combat training.
F-5D
Unbuilt trainer version.
F-5F Tiger II
Two-seat trainer version of F-5E Tiger II, AN/APQ-167 radar tested, intended to replace AN/APQ-157, but not carried out.
F-5F Tiger III
Upgraded trainer version of the F-5F in use by the Chilean Air Force.
F-5T
Upgraded F-5F in use by the Republic of Singapore Air Force.
F-5THF (บ.ข.18 ค)
Twin-seat version of F-5TH currently in active services with the Royal Thai Air Force as of May 2020.
F-5FM
Upgraded trainer version of the F-5F for the Brazilian Air Force.
Northrop F-5