Stating that "desperate measures" were required to "put things in order", aviation regulator Directorate General of Civil Aviation told IndiGo on Friday to replace the Pratt and Whitney engines under both wings of 97 A320neo aircraft "at all costs" by January 31 or they would be grounded.
Of the 97 aircraft, 23 have PW engines that have been used for more than 2,900 hours and have to be replaced in the first tranche by November 19, the Directorate General of Civil Aviation (DGCA) told the low-cost carrier.
The DGCA directive came after the airline faced four mid-air engine malfunctions in A320neo planes in the last one week, which "has caused a serious concern and resultant disruption", according to the regulator.
The DGCA had, on Monday, asked IndiGo to replace the PW engines of 16 A320neo planes, which were used for over 2,900 hours, by November 12, but it subsequently found out that seven more aircraft were flying with such engines.
"Kindly note that after that (November 19), none of these 23 aircraft, which does not have at least one LPT (low-pressure turbine) modified engine on its wings, shall be allowed for commercial operation and their schedule will suitably be curtailed till this is accomplished," the regulator said in a press note on Friday.
With a fleet of 247 planes and a share of around 48 per cent of the domestic air passenger market, IndiGo is India's largest airline.
Just three days after the company placed one of the single-largest aircraft orders with Airbus, the DGCA advised it on Friday to "stagger or defer your future (aircraft) induction plan and procure a sufficient number of modified engines to keep the existing fleet in operation".
On Tuesday, IndiGo had announced that it would buy 300 "Airbus 320neo family" planes, which comprised A320neo, A321neo and A321XLR aircraft.