Warning them of "firm" action if flights were disrupted and passengers inconvenienced, the staff notice said the agitation by the Joint Action Forum would violate the Industrial Disputes Act and "tantamount to illegal strike".

Last night, AI CMD Arvind Jadhav had written to the employees that besides wages and salary payments every month, fuel and bank liabilities like interest and principal payments, have to be paid on time.

However, the unions blamed the management of "going back on their word" to pay the salaries by Friday.

The unions had called off their proposed strike on June 30 after the management agreed to pay salaries of 70 per cent of workers by today. They were protesting the earlier decision of the management to defer the June salary by the middle of this month.

Kadiyan alleged that the company is being "damaged systematically by certain vested interests who want to sell Air India off. This we will never allow."

He also demanded a CBI enquiry into the Air India's plan to buy 68 aircraft for Rs 6,000 crore when its annual budget is Rs 7,000 crore.

"The total budget of Air India is Rs 7,000 crore and then why it decided to buy aircraft worth Rs 6,000 crore. Air India has plans to purchase 24 aircraft and Indian Airlines has plan to buy 43 aircraft. But later Air India changed its fleet plan and within 24 weeks firmed a plan to buy 68 aircraft," he said.