An IndiGo A320 neo plane that was heading from Kolkata to Pune was forced to return to Kolkata airport on Wednesday. One of the Pratt and Whitney (PW) engines of the plane stalled mid-air forcing the pilot to return to the Kolkata airport.

This is the fourth such incident involving PW engines as the low-cost carrier in a week, a source told PTI.

From October 24 to 26, IndiGo had three in-flight PW engine shutdowns, compelling the aviation regulator DGCA to visit the airline’s premises on Monday to review the maintenance and safety data.

“The Kolkata-Pune flight 6E-862 on Wednesday evening was gaining altitude and at around 9,000 feet, when one of its engines stalled. The pilot immediately turned back and brought the aircraft to the Kolkata airport. The plane is currently grounded,” the source privy to the development told news agency Press Trust of India.

The Directorate General of Civil Aviation (DGCA) directed the low-cost carrier on Monday to replace the PW engines of 16 A320neo aircraft, which were used for over 3,000 hours, within the next 15 days or face grounding of these planes.

It issued similar instructions to GoAir on Tuesday, asking it to replace the PW engines of 13 A320neo aircraft, which were used for over 3,000 hours, within the next 15 days.

“IndiGo A320neo was operating Kolkata-Pune flight 6E-862. During flight the pilot observed an engine #1 caution message. Pilot carried out the necessary checklist and returned the aircraft to Kolkata. The aircraft is currently withdrawn from operations and is under maintenance inspections. Alternate arrangements for all the passengers have been made,” a spokesperson of IndiGo said in a statement.

IndiGo has a share of 48 per cent of the domestic air passenger market which makes it the largest airline in India.

The PW engine-powered A320neo has been facing glitches since its induction in 2016. It has also resulted in grounding of some planes.