The Air India management on Tuesday warned its striking pilots to come back to work or face consequences.
"Striking pilots must return to work by 6 pm today or face action," said the management.
"A strike needs a notice in advance. The Air India pilots have called in sick. Such kind of a strike is illegal," said Singh.
"This is not appropriate. Every section has grievances, they should have some patience," he said.
The strike by the pilots is in a bid to show their protest against the decision to send domestic sector pilots for training on the Boeing 787 Dreamliner.
Four international flights have been affected by the strike. The cancelled flights include flights from Mumbai to New Jersey, New Delhi to Chicago, New Delhi to Hong Kong and New Delhi to Toronto.