The Republic of Bulgaria is now a member of NATO, during the non-declared Cold War (1947-1991) the People’s Republic of Bulgaria was a member of the Warsaw Pact. Warsaw Pact Bulgaria first received the MiG-29 during the last years of the Cold War, starting in 1989. Bulgaria joined NATO in 2004.
U.S. Air Force video report, from 13OCT2010, explaining wargame Thracian Star:
MiG-29 taxis past a Minnesota Air National Guard 148th Fighter Wing F-16, Graf Ignatievo Air Base, 26MAY2014.
A Bulgarian MiG-29UB pilot helps a Louisiana Air National Guard F-15 Eagle pilot attach his oxygen mask before a familiarization flight in a MiG-29UB during a training mission at Graf Ignatievo Air Base, 20APR2015. Louisiana Air National Guard photo by Master Sergeant Toby M. Valadie.
In May 2015, Louisiana Air National Guard F-15C Eagles trained alongside Bulgarian MiG-29s. Video by Master Sergeant Toby M. Valadie, edited by me to focus on the MiG-29:
New Jersey Air National Guard photo by Master Sergeant Andrew J. Moseley, 13JUL2015.
MiG-29UB, Graf Ignatievo Air Base, 15JUL2015. New Jersey Air National Guard photo by Master Sergeant Andrew J. Moseley.
F-16s, MiG-29 and MiG-21. New Jersey Air National Guard photo by Master Sergeant Andrew J. Moseley, 20JUL2015.
Bulgaria began NATO ‘policing’ of the Black Sea in 2016. U.S. Air Force photo by Staff Sergeant Joe W. McFadden, 08SEP2016.
USAF video, by Staff Sergeant Ashley Corkins, MiG-29s during NATO’s first ever ‘joint air policing’ (along with California & Massachusetts Air National Guard F-15 Eagles) of the Black Sea, on 09SEP2016:
Bulgaria began NATO ‘policing’ of the Black Sea in 2016. U.S. Air Force photo by Staff Sergeant Joe W. McFadden, 09SEP2016.
NATO video released 13OCT2020, showing ‘air policing’ operations over supposed NATO Black Sea territory. Video was edited by me to highlight the MiG-29:
MiG-29UB. U.S. Air Force photo by Airman First Class Brooke Moeder, 13JUL2021.
MiG-29UB excerpt from U.S. Air Force promo video (by Airman First Class Brooke Moeder, 15JUL2021):
MiG-29UB. U.S. Air Force photo by Airman First Class Brooke Moeder, 20JUL2021.
USAF Airman First Class Brooke Moeder shows you MiG-29 action during wargame Thracian Star, July 2021:
In 2019, NATO-Bulgaria paid Lockheed Martin, in full, for eight U.S. made F-16 Falcons, however, on 17MAY2023, BulgarianMilitary.com reported that the United States government/Department of Defense canceled any additional F-16 purchases and told Bulgaria to continue using the MiG-29!
On 11AUG2023, The Sofia Globe reported that NATO-Bulgaria is paying NATO-Poland 9.5-million Euros to rebuild six MiG-29s!
Cold War & Beyond: 
Микоян и Гуревич (Mikoyan & Gurevich) МиГ-29 (MiG-29)
Post Cold War:
NATO’s MiG-21s (including Bulgaria)