NEW DELHI (AP) — Chaos gripped major Indian airports Friday as passengers of the country’s biggest airline, IndiGo, scrambled to cope up with widespread flight disruptions and cancellations triggered by newly enforced rules limiting working hours for crew and pilots.

Scenes of frustration played out as passengers slept on airport floors, queued for hours at customer service counters and waited without clear communication from the airline.

Friday was the fourth straight day of disruptions as the low cost carrier struggles with new regulations that mandate longer rest periods and limit night flying hours to address concerns about fatigue and safety.

The first phase of the rules came into effect in July while the second phase kicked in November. IndiGo struggled to adapt its rosters in time, resulting in widespread cancellations and disruptions.

On Thursday, more than 300 IndiGo flights were grounded while several hundreds delayed. A passenger advisory from the Delhi airport Friday stated that all domestic IndiGo flights will remain cancelled until midnight. Other major airlines, including Air India, have not faced similar issues so far.

IndiGo operates around 2,300 flights daily and controls nearly 65% of India’s domestic aviation market.

Senior citizen Sajal Bose was scheduled to travel with his wife Senjuti Bose early Friday from Kolkata to New Delhi to attend a friend’s silver jubilee celebration. His flight was cancelled an hour before the scheduled take off.

Bose told The Associated Press he was now taking a nine-hour train ride to the city Bagdogra, where he plans to get a flight to New Delhi on another airline. “Its very irresponsible and complete negligence. Very difficult for older people like us,” he said.

In an internal email to employees this week, seen by The Associated Press, IndiGo CEO Pieter Elbers apologized, and cited technology glitches, schedule changes, adverse weather conditions, heightened congestion and the implementation of the new rules as the reasons for flight disruptions.

The Civil Aviation Ministry said in a statement that the disruptions arose primarily through misjudgment and planning gaps as the airline implemented phase two of the new rules, and that the airline acknowledged that the effect on crew strength exceeded their expectations.

IndiGo has sought temporary exemptions in implementing the new rules and told the government that corrective measures were underway. It has indicated the operations will be fully restored by Feb. 10.

More cancellations are expected in the next couple of weeks, and the airline said it would reduce its flight operations from Dec. 8 to minimize disruptions.

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Associated Press videojournalist Piyush Nagpal in New Delhi contributed to this report.