IndiGo has been given till May 31 to complete the process of replacing the unmodified Pratt and Whitney engines from its fleet. Earlier the Directorate General of Civil Aviation (DGCA) had mandated that the airline complete the removal of unmodified engines by the end of this month.

In a statement, the DGCA has said that 70 per cent of the total New Engine Option (NEO) engines of the IndiGo fleet is likely to be modified by the end of this month. ``Incidentally, the procurement of modified engines was adversely impacted due to holidays during Christmas and New Year at Maintenance Repair and Overhaul facilities,” the statement says adding that the process of placement of at least one modified engine on the entire fleet has been accomplished by Indigo, well before the timeline of 31st March this year given by the European Union's Aviation Safety agency EASA.

Four Air Turn Back (ATB)/Inflight Shut Down (IFSD) events were witnessed on Airbus 320 Neo aircraft operated by Indigo in a week during October last year due to the failure of 3rd stage LPT blades, which caused serious concern. ``At the root of the problem were the un-modified engines powering the Indigo NEO fleet and therefore, faced with an unprecedented situation, DGCA was constrained to set up a tight timeline for change of these engines,” the statement adds.

The Indian aviation watchdog decided to act as it believed that the unmodified engines contained an unsafe condition, which is prone to undesirable outcomes and therefore, needs to be dispensed with. ``This observation has been acknowledged by the global regulators, Federal Aviation Administration of the United States and EASA and therefore, both have committed to their replacement,” the statement says.

FAA had issued an Airworthiness Directive in November last year mandating removal of unmodified engines from service in the case of Indigo Airlines by November 2020.

EASA has for the time being only mandated removal of one of the unmodified engine and its replacement with a modified one on IndiGo’s complete fleet powered by P&W engines by March 2020.