Romania now uses a squadron of 17 F-16 fighter jets bought recently from Portugal, and signed a contract with Norway in November to buy 32 additional used F-16s.

At a ceremony on Monday, the MiG-21 LanceR jets embarked on their final flights.

During the communist regime, Romania had around 400 MiG-21s. The current number is confidential, but unofficial estimates say it now stands at around 25.

The retired jets will be stored at the Bacau airbase in northeast Romania.

"It was time for us to move on to something better and be in line with the world," Romanian pilot Adrian Trifa, 37, told AFP ahead of the ceremony at the Borcea airbase in the southeast.

Trifa will not train to fly the more modern jets as he is "old" -- the age to start training for F-16s is under 35, he says.

Last May, Romania said it would use its fleet of MiG-21 LanceRs for one more year for air policing missions and flight training, just a month after deciding to ground them following a slew of problems.

From 1991 to 2022, there were "30 aviation incidents that resulted in the destruction of the MiG-21 planes", according to the Defence Ministry.

In March 2022, a MiG-21 disappeared from the radar while on patrol near the Black Sea. It was later found to have crashed, killing the pilot.

NATO has strengthened its eastern flank following Russia's invasion of Ukraine, including with the supply of troop reinforcements and equipment to Romania.

Last month, Romania's supreme defence council said it aimed to buy the latest generation of American F-35 fighter jets, but it will likely take years for the acquisition to go ahead.

Retired general Stefan Danila, a former chief of defence and former MiG-21 LanceR pilot, said the shift to more advanced jets should have happened "at least ten years ago".

"It is being made late, very late," Danila said, adding that some of the retired aircrafts still have some flight hours in them and could be sold to other states to be used for military exercises.

"Ukraine didn't express interest in these aircrafts," however, he added.