Fuerza Aerea Argentina / Argentine Air Force
The Argentine Air Force showed interest in July 2015 to buy Northrop F-5s, together with Beech T-34, in order to replace withdrawn GAMD Mirages and establish a regional balance as Brazil and Chile already operated Northrop F-5s. Original request for a Squadron of XXX F-16 was  not acceptable to the USA. A delegation to the United States studied the possiblity to buy 12/14 former Swiss AF/US Navy Northrop F-5N in 2016. Selectioned was finally the GAMD Super Etendards.
Fuerza Aerea Boliviana / Bolivian Air Force
On 30-09-74 a Northrop delegation presented to the commander of the Bolivian Air Force/Army/Navy a briefing (at the request of the local Air Force) about the Northrop F-5E, without knowledge of USA State, Defence and Embassy Departments. According Northrop the briefing was not in order to sell the aircraft, but price and delivery time were confidential. Opposition was expressed by US representative as, according to the information of the Bolivian Head of State. the country wished to concentrate on buying transport aircrafts.
The Bolivian Air Force mentioned they had USD 80m at disposal to buy 20 Northrop F-5E and 4 F-5F. Sale was not concluded.
Ilmavoimat / Finnish Air Force
A telex from the USA dated May 1964 informed the local embassy that Finland might have been interested in the purchase of Northrop F-5A; though not at a sophistication level as the Saab J-35 it was less expensive and might have been supported by Norway with its NorthropF-5s. It considered the purchase of either aircraft not feasable, but wanted to keep US aircraft under Finnish consideration. On 06-05-65 it was reported that the country bought Saab J-35 or maybe interested in the Mikoyan-Gurevitch MiG-21. The Freedom Fighter was out of run
Indian Air Force
A letter of offer was sent xxx by the US Deputy Secretary of Defence to the Indian Minister of Defence offering its governement owned portion of an Northrop F-5 tooling facility at 5 percent of its value. This wouldhave enabled India to build 90% of the center fuselage, 80% of the forward fuselage, 50% of the wings and fuselage, 40% of the test tools for an Northrop TF-5 trainer. In 1981 India sought to buy Northrop F-5G but this was denied on gound of Pentagon's reluctance to release classified information relating to the engine.
Israel Air Force
Preferred options in a study ro replace GAMD S Mytere, Mistere, Ouragan were Northrop F-5s, Douglas A-4. Finally the latter was chosen.
Kuwait Air Force
Douglas received in March 1964 the authorisation to make uclassiffied sales presentationon
on Douglas A-4 and Northrop F-5s in September 1963; Kuwait preferred to buy one aircrafts for the interception and one for the ground attack role (English Electric Lightnings and  BAC Strikemasters).
Nigerian Air Force
During 1973 Northrop contacted Nigeria regarding the possible FMS, cash sale of 15 Northrop F-5E, but supply of Sidewinder air-to-air missile was opposed by the USA due to its policy not to deliver missiles to African countries. Northrop Tiger was in competition with Mikoyan-Gurevitch MiG-21 which was preferred.

Peru Air Force
Peru had concluded by October 1967 a contract for Mirage 5 when a conversation between the Peruvian President and the USA Ambassador took place. This mentioned if Northrop F-5s added to a loan of USD 40m could substitute the French aircraft, though this offer did not have much chances. The Perruvian kept the contract for Mirage 5 fighters.

Portuguese Air Force
The commander of the Portueguese AF expressed in June 1974 its interest in acquiring 1 Squadron of Northrop F-5s, 1 Squadron of McDonnell F-4s as well as for Northrop T-38 to replace North American F-86F and Lockheed T-33A. This was modified during on 30-07-74 during a meeting regarding the use of Lajes AFB by the USA to only 16 Northrop F-5E and 16 Northrop T-38A. By 1976 the Tiger was the preferred aircraft by the military command.  On a meeting with a US delegation on 15-11-79 the AF Command discussed the purchase of 20 Northrop F-5s to be deliverd between May and October 1981 under a Foreign Military Sales Progamm loan, but the amount due to be paid by Portugal was too high. A second proposal for 12 F-5s to be delivered between May and August 1981 was still too high. Finally only twelve Northrop T-38A for pilot supersonic training were obtained starting from 1977 together with 30 ground-attack Chance Vought A-7A.
The Air Force was still interested in buying fighter to supplant the North American F-86F used. A delegation was sent to Norwayin July 1979 to evaluate Freedom Fighters of the Norwegian AF. This was protracted till 1982 when 11 Northrop F-5A were offered at a low price, but needed repairs due to cracks found in the airframe to be paid by Portugal; double-seaters were not on offer. Only in 1984 the USA offered 4 Northrop F-5A with spare engines, offer declined due to the high number of flight hours on the aircrafts.

Qatar Air Force
Several questions regarding the Northrop F-5 were asked on 12-06-77 to the US Ambassador by the Amir during a meeting. The Amir confused the General Dynamic F-16 with the Tiger, recently shown to him beginning 1976 in Saudi Arabia. The US ambassador cleared the error and the Amir, but was unable to confirm if the fighter  sale was permissible under US Gulf arms supply policy. No other information is available. 
Salvador Air Force
Miltary personnel and civilians in USA and El Salvador wanted to upgrade the Air Force to operate Northorp F-5s. Out of question for the USA.
Uruguay Air Force
The Air Force had in 2009 shown interest (without conclusion due to dunding problems) for the Northrop F-5 when 3 IAI/Northrop F-5E Tiger III and 1 IAI/Northrop F-5F were shown in Montevideo on 17-03-13 during the 100th anniversary of local aviaiton. Unofficially was stated that the cost between 4 and 6 fighters would be around USD 80m. Also considered was the purchase from Switzeland of Northrop F-5R. Other aircrafts examined were the Russian Yak-130 and the Chinese L-15 trainer/attack aircrafts. All these alternatives were too expensive and no new aircraft was bought.