New Delhi, May 21 (IANS): The Indian Air Force (IAF) has decided to ground the entire fleet of MiG-21 fighter jets that have been in service for over five decades.

The Russia-made jets will stay grounded until investigation determines the cause of the crash of one of the Mig-21s in Rajasthan earlier this month.

On May 8, a Mig-21 Bison, shortly after taking off from Suratgarh airbase in Rajasthan, crashed near Hanumangarh.

Even as the pilot survived, three other persons were killed.

The IAF is also in the process of phasing out the Mig-21 aircraft from its fleet. In the next two years, these jets will be pulled out of service.

The Mig-21 was inducted into the IAF in the 1960s. The crash rates of these jets have also been a cause of concern.

An official said that the entire fleet of MiG-21 aircraft is being investigated.

"The main objective of the investigation is to find out the cause of the accidents involving these aircraft. The MiG-21 has been grounded till the investigation is completed and the exact cause of the accident is ascertained," the official said.

According to Defence Ministry officials, only three MiG-21 squadrons are currently operational in the IAF and all of them will be phased out by early 2025.