Air travel across India was in turmoil for a fourth day on Friday after IndiGo cancelled around 500 flights, including all departures from New Delhi, prompting the government to announce special relief measures for the country's largest airline.

In a bid to improve air travel safety, Indian authorities have introduced new stricter regulations limiting pilot flying times and placing tighter restrictions on their operation of night-time flights.

But IndiGo admitted it failed to plan properly ahead of a November 1 deadline for the measures' introduction. And with air travel now approaching its December peak, that has forced widespread flight cancellations this week that have stranded thousands of travellers.

On Friday, the airline, which accounts for over 60% of domestic air travel in the world's most populous nation, apologised to its customers.

"These last few days we have a serious operational crisis," it said in a statement. "While this will not get resolved overnight, we assure you we will do everything in our capacity to help you in the meantime."

Following a request by IndiGo, India's civil aviation authorities granted it a temporary exemption from some of the new rules on Friday to help it deal with the crisis.

IndiGo had earlier flagged that it did not expect to fully restore operations until February 10, though on Friday it said there should be "progressive improvement" from Saturday.

Other major Indian airlines, including Air India and Akasa, have not had to cancel flights due to the new rules.

Hundreds of flights cancelled, passengers vent anger

On Friday, Delhi airport announced all IndiGo departures were canceled for the day, a number that a source put at 235 flights. Chennai airport also announced all departing IndiGo flights were annulled.

The airline cancelled 165 flights in Mumbai, 102 in Bengaluru, 92 in Hyderabad, airport sources, who declined to be named, said. Other major metro airports saw IndiGo flights up to 6 p.m. (1230 GMT) cancelled on Friday.

At many airports across the country, crowds of stranded passengers voiced their frustrations, aggressively arguing with staff.

Social media platforms and local media were flooded with videos of angry travellers.

"Down with IndiGo! Down with IndiGo!" a group of passengers at Bengaluru airport shouted in protest, a video post on X showed.

Another video showed a father shouting at IndiGo crew members, demanding a sanitary pad for his daughter.

A post on X from earlier Friday morning showed dozens of young children sitting inside a Delhi airport terminal.

"Kids waiting since 4am for their IndiGo (flight) ... hungry, tired, sleepy," read the post's caption.

Indigo receives exemptions from new pilot duty rules

Shares of IndiGo dropped nearly 3% on Friday, taking their weekly slump to 10.3%. India's main opposition party has demanded a discussion on the issue in parliament.

The new pilot duty rules mandate that pilots can only make two night-time landings per week, down from six previously.

That provision was put on hold for IndiGo until February 10 by India's civil aviation regulator. The airline was also temporarily exempted from a rule specifying maximum flight duty periods for pilots doing some night flying.

IndiGo said it will offer waivers on all cancellations and booking changes for travel between December 5 and December 15. The airline has also arranged ground transportation and thousands of hotel rooms for stranded customers, it said.