To replace its Soviet-era MiG-29 jets, Bulgaria has ordered 16 American F-16s for a cost of around 2.4 billion euros ($2.7 billion), in the largest contract to overhaul its armed forces since the fall of communism in 1989.

At a ceremony marking the jet's delivery at the Graf Ignatievo military base in central Bulgaria, Prime Minister Rossen Jeliazkov said those in attendance were celebrating "the inexorable and irreversible modernisation of the Bulgarian army.

US defence official David Baker hailed the jet's delivery as a "significant milestone".

"Your investments today will improve Bulgaria's security for decades to come and enable you to further contribute to making NATO the greatest military alliance in history," Baker added.

After the first delivery on Sunday, seven more F-16s are due to be delivered by the end of 2025, with the remaining eight to arrive by 2027.

Bulgaria, which last year celebrated the 20th anniversary of its entry into NATO, has for a long time delayed the modernisation of its air force for political and financial reasons.

But as with other eastern members of the US-led defence alliance Russia's invasion of Ukraine has forced a rethink of its defence posture.

The poorest member of the European Union now spends more than the NATO-baseline two percent of national output on defence -- though still well below the five percent now demanded by US President Donald Trump.

As a result of its ageing fleet, the country's fighter pilots lack training, according to a 2024 government report, which also pointed to a dearth of qualified personnel.

In June 2021, a Bulgarian pilot died after his MiG-29 crashed during a military drill in the Black Sea.

In September 2024, two more soldiers were killed during a training flight for an air show.