India’s competition regulator said on Thursday it was reviewing allegations of antitrust violations by budget airline IndiGo following recent flight disruptions that hit air travel nationwide.

The airline, which controls more than 60% of India’s domestic market, cancelled about 4,500 flights earlier this month due to poor pilot roster planning, stranding tens of thousands of passengers and triggering one of the country’s biggest aviation crises. Fares surged during the cancellations, prompting the government to impose temporary caps.

The Competition Commission of India said it had “taken cognisance of information filed against IndiGo in the context of the recent flight disruptions witnessed in the aviation sector, across various routes” and decided to proceed with an initial assessment. It did not disclose details of the allegations.

One complaint, seen by Reuters, accuses IndiGo of cancelling flights and then offering seats at much higher prices, amounting to abuse of its dominant market position. The filing by lawyer Kartikeya Rawal alleges his ticket was cancelled and the replacement fare quoted was significantly higher.

IndiGo did not immediately respond to a request for comment.

The disruptions underscored the risks of a near-duopoly in the world’s fastest-growing aviation market, where IndiGo and Air India together hold a more than 90% share.

The CCI did not respond to a request for comment beyond its statement. In such cases, the regulator can order a detailed probe that may lead to penalties if wrongdoing is established.

IndiGo, known for its on-time performance, has apologised for the cancellations, calling them a “blemish” on its record.