The airport in eastern Calcutta city has been worst affected
Many domestic airline flights have been cancelled in India after some airport workers went on strike against the government's economic policies.
The strikers, belonging to communist unions, are particularly opposed to the privatisation of airports.
Banks around the country have also been affected after three bank unions went on strike against feared job cuts.
Airline and bank workers in India have gone on strike before to protest against reforms in their industries.
A number of flights from the Indian capital, Delhi, have been cancelled because of the 12-hour strike which began at 0700 IST (0130 GMT) .
The airport in the eastern Indian city of Calcutta was the worst affected with all flights cancelled. Calcutta is the capital of West Bengal state, which is ruled by communists.
Reports said that air force personnel has been deployed at some airports to keep them running.
Three public and private bank unions, which claim to represent some 600,000 workers are protesting against planned mergers of banks, which they fear will lead to job cuts.
"The government is hurriedly pursuing mergers without addressing our concerns," bank union leader CH Venkatachalam told the Reuters news agency.