India's biggest airline IndiGo says operations 'back to normal'

"Our on-time performance is... back to normal levels," an IndiGo statement said, adding the airline was operating more than 1,800 flights on Tuesday, and planned to "fly nearly 1,900 flights" on Wednesday.

But India's civil aviation regulator told the company to cut its planned flights by 10 percent as it had "not demonstrated an ability to operate these schedules efficiently".

A previous order called for a five-percent reduction.

Civil aviation minister Ram Mohan Naidu said it was "necessary to curtail the overall IndiGo routes, which will help in stabilising the airline's operations and lead to reduced cancellations".

Airports across India were thrown into disarray last week, with the private carrier admitting "misjudgement and planning gaps" in adapting to a new pilot rest policy which has since been suspended.

The operational meltdown came even though IndiGo had two years to prepare for the the new rules, which came into effect last month with the aim of giving pilots more rest periods to enhance passenger safety.

Naidu last week said the flight duty time limitations rules had "been placed in abeyance".

The minister told parliament on Tuesday that a "detailed enforcement investigation" into the disruption had begun.

"No airline, however large, will be permitted to cause such hardship to passengers through planning failures, non-compliance or non-adherence to statutory provisions," Naidu said.

"Safety in civil aviation is completely non-negotiable."

The crisis is one of the biggest challenges faced by IndiGo, a no-frills airline which has built its reputation on punctuality.

India is one of the world's fastest growing aviation markets, hitting 500,000 daily flyers last month for the first time.