Explained | New pilot roster rule or tech glitch and weather? Why over 100 IndiGo flights cancelled in one day

India's largest airline, IndiGo, saw over a 100 flights being cancelled and several other flights being delayed on Tuesday and Wednesday.

Flights across major airports were affected with thousands of passengers left stranded, leading to long queues at terminals, in what is one of the most jarring operation disruptions in recent years. Passengers and authorities alike questioned the reason for the sudden collapse.

In a statement released by the low-cost airline on Wednesday, it was explained that the cancellations and delays were due to a combination of reasons like minor technology glitches, schedule changes linked to the winter season, adverse weather conditions, increased congestion in the aviation system and the implementation of updated crew rostering rules (Flight Duty Time Limitations).

The airline added that it had made adjustments to schedules to control the disruption and that operations would be normal in the next 48 hours.

"Our teams are working around the clock to ease customer discomfort and ensure operations stabilize as quickly as possible. Furthermore, the affected customers are being offered alternate travel arrangements to reach their destinations or refunds, as applicable," the airline said in a press release.

Further, the Ministry of civil aviation said that the airline had provided a detailed reply to the inquiry into the disruption.

Reasons for cancellations

According to the airline, a total of 1,232 flights were cancelled in November. A large share of cancellations arose from crew / FDTL compliance and airport/airspace/ATC-related factors, many of which lie beyond the operator’s direct control. The airline's overall on-time performance for November was 67.70% as compared to 84.1% in October.

Of the 1,232 cancellation, the airline said 755 were due to crew/FDTL constraints, 92 were because of ATC, another 258 because of airport and airspace restrictions, and 127 for other reasons.

Why the crew shortage?

IndiGo has been grappling acute pilot and cabin crew shortage following new, stricter duty-time regulations that came into effect on November 1.

The updated rules significantly reduce the number of hours pilots can fly and increased mandatory rest requirements.

According to the new norms, The DGCA caps flight time to: eight hours per day, 35 hours per week, 125 hours per month and 1,000 hours per year

Additionally, crew must also receive rest periods equal to twice the duration of their flight duties, with a minimum of 10 hours of rest within any 24-hour window.

What were the technical glitches?

On Tuesday, major airports like Delhi, Pune and Bengaluru reported failures in their check-in and departure control systems, creating long queues and delaying departures across multiple airlines, including IndiGo.

How does winter air traffic affect flights?

High passenger volumes, winter fog-related issues on operations, and peak-hour congestion at major metro airports affected operations.

IndiGo's website states that the airline operates "well over 2,200 daily flights." Government data showed its on-time performance had plunged to just 35 per cent, implying that more than 1,400 flights were delayed on a single day.