Historically, Mig-21 fighters have had a poor track record when it comes to flight safety. Due to its poor safety record, the Russian-origin fighter aircraft has been given the tag, “Flying Coffin” in popular discourse. The worst failure reported and also the most frequent is fuel leakage inside the turbo jet that ends in turbo fan explosion frequently killing or seriously injuring the pilot who’s sitting right on top of the engine. Till now, more than 170 Indian aviators and 40 civilians have died in MiG-21 crashes since 1970. Between 2003 and 2013, 38 MiG 21 fighter jets were lost in crashes. In 2002, a MiG-21 crashed into an office building in Jalandhar, killing 8 and injuring 17. The cause of the accident was a technical error. MIG 21 does have an issue, being single engine and designed almost like a rocket it has a good chance to loose altitude and control with barrel rolls or turns ( with small wings) therefore good expert pilots too sometimes could not gain back control over the aircraft in the event of a bird hit or miscalculations. We also need a supply of spares and parts, with the jets now ageing, the challenge is both technological and economic. This affects the reliability and availability of aircraft
