New Delhi, May 8 (PTI): Four international flights were cancelled after nearly 100 Air India pilots reported 'sick', officials said Tuesday, even as Civil Aviation Minister Ajit Singh called their protest illegal.

Since morning, the beleaguered Air India axed two flights from Mumbai and New Delhi each and encountered severe disruption on other routes since midnight

Monday, an official said.

Ajit Singh said "this strike illegal".

"There are certain ways of even going on strike. The pilots may have grievances but they should have spoken to the management, to me and other well wishers," he said.

"How can they (pilots) go on strike when Air India is on the path of recovery and when it is not out of the woods?"

His comments came as a section of pilots reported sick Tuesday, leading to serious disruptions in flights.

An Air India official told IANS that the Ahmedabad-Mumbai-Newark service and Mumbai-Delhi-Hong Kong flights scheduled to leave early Tuesday have been cancelled due to non-availability of pilots.

Similarly, the New Delhi-Toronto and New Delhi-Chicago flights were also cancelled.

The official added that nearly 100 pilots have remained off duty since midnight as they suddenly fell 'sick' and more were likely to follow suit.

Among other things, the pilots are opposing the carrier's plans to provide Boeing-787 Dreamliner to the erstwhile Indian Airlines pilots who are now part of the airline.

Ajit Singh dismissed this as unfair.

He said while the Delhi High Court had upheld the contention that the erstwhile Indian Airlines pilots cannot be trained on the Dreamliner, the Supreme Court had vacated the stay.

"How can the protesting pilots expect the government to go against the Supreme Court?" he said.

The action by pilots has come at a critical juncture when the airline was hoping the retrieve lost ground with the peak vacation season and had secured a whopping Rs.42,000-crore bailout package.