In September 1962 Yugoslav Air Force received first MiG-21F-13 fighters (in Yugoslav military designated as L-12).  
In the period from 1962 to the early 80s Yugoslavia had bought about 216 MiG-21 aircraft in 9 variants - MiG-21F-13 Fishbed-C (L-12), MiG-21U-400 and U-600 Mongol-A (L-12 and NL-12M), MiG-21PFM Fishbed-F (L-14), MiG21US Mongol-B (NL-14), MiG-21R Fishbed-H (L-14i), MiG-21M Fishbed-J (L-15), MiG-21MF Fishbed-J (L-15M), MiG-21UM Mongol-B (NL-16) and MiG-21bis Fishbed-N and Fishbed-L (L-17 and L-17K).  
From 1964 to 1992 about 80 aircraft had been lost in accidents. Yugoslav Air force units that operated MiG-21 were 204th fighter-aviation regiment at Batajnica Air Base (126th, 127th and 128th fighter-aviation squadrons), 117th fighter-aviation regiment at Željava Air Base (124th and 125th fighter-aviation squadron and 352nd recon squadron), 83rd fighter-aviation regiment at Slatina Air Base (123rd and 130th fighter aviation squadron), 185th fighter-bomber-aviation squadron (129th fighter-aviation squadron) at Pula and 129th training center at Batajnica air base. 
  
All the Yugoslav MiG-21s which have evacuated to Serbia after 1992 have continued their service in the FR Yugoslav Air Force. During the 1999 NATO attack on FRY, Yugoslav Air Force lost 33 MiG-21s on the ground. 
  
Units armed with MiG-21F-13 was transfered to PFM in 1970. 
  
Famous third generation MiG-21's are the M's and MF's. The MiG-21M was the first export version of the SM and had the older R-11F2S-300 engine and still the RP-21 radar as opposed to the more sophisticated Soviet SM variant. The MiG-21M (NATO Fishbed J) probably was the most unliked version (by pilots) of the MiG-21. It could carry 2650 liters (700 gal) of internal fuel as well as three 490 liter drop tanks, or one 800 liter (211 gal), and two AAM's (four AAM's with the 800 liter drop tank) on four under wing hard points. It also had an internal GSch-23 twin-barrel cannon with 200 rounds. It now was a considerably heavier aircraft with serious performance shortages.  
  
That lead to the development of the MiG-21MF with an uprated R-13-300 engine with 14550 lbs of thrust. Soviet MF's(SM) also had the more advanced RP-22 radar. Improvements from M to MF's included the new AP-155 Autopilot, a truly 3-axis autopilot with altitude hold, unusual attitude recovery, and automatic terrain clearance hold. MiG-21SM's saw considerably combat in Afghanistan and export MF's in the Iran-Iraq war (one kill against an Iran F-14 Tomcat). MiG-21M's were also built in India under license and China (MF) without license. This aircraft features western avionics and have the option of carrying the French Matra Magic AAM in addition to the normal Chinese AIM-9 Sidewinder copies. Another third generation MiG-21 was the SMT (NATO Fishbed K), flown only by Soviet Air Force pilots. Production was short lived (between 1971 and 1972)The enlarged dorsal spine (to carry more fuel, 3250 liter internal) had adverse effects on the aircraft's flight characteristics.