New Delhi, Dec. 5 -- At least 250 IndiGo flights were cancelled on Thursday as chaos continued at major airports across India, with the carrier struggling to adapt to stringent new crew rostering rules. On Wednesday, the airline cancelled at least 150 flights and announced that it had initiated "calibrated adjustments" to its schedules for the next 48 hours. The on-time performance (OTP) of IndiGo, India's largest airline, dropped to 19.7% on Wednesday from 35% a day earlier, according to civil aviation ministry data. An official aware of the matter said 33 flights were cancelled from Delhi, 68 from Hyderabad, 85 from Mumbai, and 73 from Bengaluru on Thursday. On Wednesday, at least 67 flights were cancelled at Delhi airport (37 departures and 30 arrivals), 42 at Bengaluru, 40 at Hyderabad (19 departures and 21 arrivals), and 33 at Mumbai (17 departures and 16 arrivals). In a statement on Wednesday, IndiGo said calibrated adjustments will remain in place for the next 48 hours and will normalise operations and progressively recover punctuality across the network. "Our teams are working around the clock to ease customer discomfort and ensure operations stabilize as quickly as possible." The airline said the affected customers are being offered alternate travel arrangements to reach their destinations or refunds, as applicable. The airline did not issue an update on its flight operations on Thursday. Technology glitches, adverse weather, increased congestion, and the implementation of updated Flight Duty Time Limitations (FDTL) that came into force in November triggered the chaos. An emergency Airbus A320 software patch rushed through over the weekend of November 29-30 disrupted crew scheduling just as the airline was operating with minimal slack due to the FDTL rules. The Directorate General of Civil Aviation (DGCA) data showed the airline had been under strain, having cancelled 1,232 flights in November-755 of them attributed to FDTL issues-with OTP dropping to 67.70% from 84.1% in October. IndiGo's baggage systems at Delhi's Terminal 1 and Terminal 3 encountered problems on Wednesday, compounding the aviation chaos. Flights were scrapped as passengers turned up to check in. Many said they missed onward connections. New FDTL norms were implemented in two phases on July 1 and November 1. The rules have been designed to combat fatigue and boost rest periods. They mandated an increase of weekly rest periods to 48 hours, extension of night hours, and limited the number of night landings to two, down from six earlier. The DGCA said on Wednesday it was investigating the situation and had summoned IndiGo to its headquarters "to present the facts leading to the current situation along with plans to mitigate the ongoing delays and cancellations". The airline operates around 2,200-2,300 flights daily to over 90 domestic and 45 international destinations As of December 2, IndiGo had a total of 416 aircraft in its fleet, with 366 in operations and 50 on ground, up from 47 the previous month, according to aircraft fleet tracking website Planespotter.net. The Airline Pilots Association of India, which represents over 800 pilots, on Wednesday criticised what it called "a failure of proactive resource planning" by dominant airlines. IndiGo's OTP of just 35% on Tuesday was the lowest among Indian carriers and a steep fall from its typical 80%-plus performance at major airports. Ameya Joshi, an aviation analyst and former network planner, said IndiGo is not just the largest carrier but also has substantial flights during the nighttime, which now require additional rest....