The aircraft arrived over Nagpur. The flight crew began to carry out ‘approach’ check list. While configuring the aircraft during the approach checks, the flight crew realized that landing gears were in extended position and were not retracted after take-off from Kolkata. The aircraft landed safely at Nagpur at 0631 UTC. The flight crew reported in PDR that the reason for diversion was insufficient fuel. The AME carried out inspection for fuel leak. There was no fuel leak and no abnormality detected in the aircraft. The aircraft was refuelled and released for onward flight to Mumbai. The aircraft landed safely at Mumbai airport.