Aviation safety regulator DGCA on Monday said it has received IndiGo's response to the show cause notice issued over the large-scale flight cancellations and will take enforcement action.

It also said that the airline is "profusely apologetic" and deeply regrets the inconvenience and hardship caused to customers following flight cancellations.

DGCA said it is in the process of examining the response, and enforcement action, as deemed appropriate, will be taken in due course.

The regulator had on Saturday issued show cause notices to IndiGo CEO Pieter Elbers and Accountable Manager Isidro Porqueras seeking explanations within 24 hours on the massive flight disruptions.

This was later extended to Monday, 6 pm, after the airline sought more time from the regulator.

"IndiGo submitted replies signed by both Chief Executive Officer and Chief Operating Officer on December 8 at 1801 hours," the DGCA said in a statement.

IndiGo, in its response, said the disruption resulted from a combination of the factors, including minor technical glitches, schedule changes linked to the start of the winter season, adverse weather conditions and increased congestion in the aviation system as well as implementation of and operation under the updated crew rostering rules (Flight Duty Time Limitation Phase II) -- which coincided in lesser or greater measure, as per the statement.

The airline, in its response, stated that "it is realistically not possible to pinpoint the exact cause(s) at this time due to the complexity and vast scale of operations".

It also noted that the DGCA's manual allows a fifteen-day response time for show-cause notices, suggesting more time is needed to conduct a comprehensive 'Root Cause Analysis' (RCA).

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