IndiGo and GoAir grounded nine Airbus A320neo aircraft on account of trouble with the engines manufactured by United Technologies’ Pratt & Whitney, PTI reported, quoting a Directorate General of Civil Aviation statement on Friday. Civil Aviation Minister Suresh Prabhu has asked the Directorate General of Civil Aviation to submit a detailed report on the matter.

The development follows the grounding of five Airbus A320neo aircraft owned by IndiGo operator InterGlobe Aviation in July for the same reasons, Reuters had reported. IndiGo’s operator had then said that the aircraft were scheduled to be back in service by the second half of August.

The Directorate General of Civil Aviation said seven IndiGo and two GoAir aircraft were grounded on August 24. “At present, there are 60 A320 neos with Pratt & Whitney engines [41 with IndiGo and 19 with GoAir],” the statement said. The groundings have been attributed to “combustor distress found during routine scheduled boroscopic inspections”.

The inspection includes the use of a boroscope – a device used to examine parts that are inaccessible.

In his directive to the civil aviation regulator, Prabhu stressed on the importance of the security of passengers. The Directorate General said aircraft are removed from service when combustor distress is detected.

“A320 neos inducted after March 2018 are coming with P&W engines fitted with Block C combustors which has better life,” the regulator said. “The manufacturers have taken measures to address significant problems of engines related to combustion chambers distress and No 3 bearing issues by replacing Block B combustion chambers with Block C and providing dry face bearing seals. These measures have significantly reduced the engine problems.”

In February and March, the aviation regulator directed IndiGo to ground eight of its flights due to safety concerns. The company has had several changes recently. On April 27, the company told the stock exchanges that its president and director, Aditya Ghosh, was stepping down. Several other changes have been made in the top management as well.