The Airport Authority of India Employees Joint Forum on Tuesday threatened to stop work immediately after formal announcement of the modernisation contracts.
The threat comes amid the ongoing process of opening financial bids for awarding contracts for modernisation of Delhi and Mumbai airports.
Meanwhile, the government is understood to have asked the Indian Air Force to standby for any contingency.
As soon formal announcement of the bids are made, airport employees and officers across the country would stop work, MK Ghoshal, Convenor of the AAI Employees Joint Forum said.
"Whether you call it a strike or boycott, it doesn't matter. We have informed the minister. All the unions across the country are prepared for it," he said.
Reports reaching here said the housekeeping, ground operations, storekeeping employees of Mumbai airport have already stopped work. However, there were no reports of flight disruptions.
In Kolkata, employees were shouting slogans inside the airport.
In Delhi also, airport employees protested.