New Delhi/Mumbai: The country's largest airline IndiGo on Thursday cancelled more than 550 domestic and international flights, and services were delayed at various airports as operational disruptions continued for the third straight day, impacting travel plans of hundreds of passengers.

On a day when the civil aviation ministry and watchdog DGCA held a meeting with senior IndiGo officials to take stock of the situation as well as the mitigation plans, the airline's CEO, Pieter Elbers, told the staff that normalising operations and bringing back punctuality will not be an "easy target".

The airline, which generally operates around 2,300 flights daily and presents its punctuality as a hallmark, recorded an on time performance of 19.7 per cent on Wednesday, a steep fall from 35 per cent reported on Tuesday. Grappling with significant flight disruptions due to a multitude of factors, including cabin crew woes and technology issues, the airline has adjusted its schedules which means that pre-planned service cancellations are being carried out as part of normalising operations.

Sources told PTI that more than 550 flights were cancelled at different airports, including 172 flights at the Delhi airport, on Thursday.

There were at least 118 flight cancellations at the Mumbai airport, 100 at Bangalore, 75 at Hyderabad, 35 at Kolkata, 26 at Chennai, and 11 at Goa. Flight cancellations were reported at other airports also. "IndiGo has been experiencing a sharp rise in cancellations, reaching approximately 170-200 flights per day, which is substantially higher than normal," the Directorate General of Civil Aviation (DGCA) said in a statement Based on data from six key airports -- Delhi, Mumbai, Chennai, Kolkata, Bengaluru and Hyderabad -- IndiGo's OTP nosedived to 19.7 per cent on Wednesday, down from 35 per cent on December 2.

The sources said the Directorate General of Civil Aviation (DGCA) is meeting the airline officials to discuss the situation.

In late afternoon trade, IndiGo shares dropped over 3 per cent to Rs 5,417.90 apiece on the BSE.

On Wednesday, DGCA said it was investigating IndiGo flight disruptions and has asked the airline to submit the reasons for the current situation, as well as its plans to reduce flight cancellations and delays. The sources said the airline has been facing an acute crew shortage since the implementation of the second phase of the FDTL (Flight Duty Time Limitations) norms.

While IndiGo has not issued any statement on Thursday, the airline, which operates around 2,300 domestic and international flights daily, on Wednesday said a "multitude of unforeseen operational challenges" have significantly disrupted its operations across the network for the past two days, and apologised to the passengers for the inconvenience.

The airline is adjusting its schedules in a calibrated manner to normalise the situation.

The Federation of Indian Pilots (FIP) has alleged that IndiGo, despite getting a two-year preparatory window before the full implementation of new flight duty and rest period norms for cockpit crew, 'inexplicably' adopted a 'hiring freeze'.Further, the pilots' grouping has urged DGCA not to approve airlines' seasonal flight schedules unless they have adequate staff to operate their services 'safely and reliably' in accordance with the new FDTL norms.