The announcement came one day after the Romanian military reported that a MiG-21 jet experienced a problem with its landing gear.

"The measure was taken because of the considerable number of incidences and aviation accidents reported while using the MiG-21 LanceR," the ministry said.

On March 2, a MiG-21 disappeared from the radar while on patrol near the Black Sea. It was later found crashed with the pilot killed.

An IAR 330-Puma helicopter searching for the jet crashed in bad weather, killing all seven crew on board.

A "combination of human and environmental factors" caused the crashes, the defence ministry said in a preliminary investigation.

The precise number of MiG-21 fighter jets is confidential. Unofficial estimates put the number at around 25 in Romania today. During the communist regime, the country had around 400 MiG-21s.

Friday's announcement leaves the NATO member dependent on a squadron of F-16 jets bought recently from Portugal and on allied air policing missions.

NATO strengthened its eastern flank following Russia's invasion of Ukraine, which has included sending troop reinforcements and equipment to Romania, which shares a border with Ukraine.

Bucharest also says that it has "accelerated" efforts to buy another 32 F-16 jets from Norway, adding two more squadrons to the country's air force.