A general strike is expected to shut down many public services and disrupt mass transit systems in Portugal as workers contest austerity measures linked to a euro78 billion ($104 billion) bailout.
Officials say international flights could be canceled during Thursday's protest, and few train services are scheduled to run.
Government offices, school classes, mail deliveries and trash collections are also likely to be severely affected.
The government has enacted tax hikes and cuts in pay and welfare entitlements as it tries to drive down the recession-hit country's high debts.
Portugal's two largest trade union confederations, representing more than 1 million mostly blue-collar workers, said Wednesday they also planned 34 protest marches across the country.