The airline must replace all Pratt & Whitney engines in its fleet of almost 100 twin-engined Airbus A320neo planes.

IndiGo airlines must replace all Pratt & Whitney (P&W) engines in its fleet of almost 100 twin-engined Airbus A320neo family aircraft with new P&W power units, India’s air safety watchdog said on Friday following recent in-flight engine shutdowns.

The incidents have caused “serious concern” and the decision to order the engines to be replaced was taken after “considerable deliberations”, India’s Directorate General of Civil Aviation (DGCA) said in a statement.

“You will appreciate that four successive events have not happened ever before, and therefore, we call for urgent and effective action. We regret the inconvenience, but we need desperate measures to put things in order,” the DGCA said.

“This situation cannot be allowed to go on indefinitely,” it said, adding that the engines would need to be replaced by January 31, 2020.

IndiGo is Airbus’s biggest client for A320neo planes.

Though the engines made by Pratt & Whitney, a United Technologies subsidiary, are fuel-efficient, there have been issues since they entered into service in 2016, forcing IndiGo to ground its planes several times.

The groundings have cost the airline, which last month posted its biggest-ever quarterly loss after being forced to lease aircraft to replace planes grounded with engine issues.

IndiGo said it currently operates a fleet of 98 A320neo family planes in which around 45 percent of its engines are modified.

“We are working with both P&W and Airbus on mitigation so that we have enough modified spare engines by January 31, 2020. In the meantime, our schedule remains intact,” the company said in a statement to stock exchanges.

On Monday the DGCA ordered IndiGo and domestic rival GoAir to modify 29 Airbus A320neo aircraft fitted with Pratt & Whitney engines within 15 days to avoid them being grounded.

The DGCA said that planes fitted with Pratt & Whitney 1100 series engines that have clocked more than 2,900 hours must have at least one modified engine, impacting 16 of IndiGo’s planes.

In its statement on Friday, the DGCA said seven more of IndiGo’s planes had been found to have the same issue, taking the total to 23. It has asked the airline to replace at least one engine on these 23 planes by November 19, and IndiGo would then need to replace both engines on its entire A320neo fleet.

DGCA chief Arun Kumar, who was recently appointed to the position, is making the right decisions relating to safety, said Kapil Kaul, India CEO at consultancy CAPA.

“This gives time for these engine changes to be completed and yet remains firm on safety,” said Kaul, adding that Pratt & Whitney would need to ensure that all engines are replaced by the deadline.