Olympic Airlines, currently being privatized, have cancelled 75 flights, including 11 to Europe and Turkey, while its privately-owned rival Aegean Airlines is cancelling 22 flights to internal destinations and Cyprus because of strike action by staff and a four-hour walk-out by air traffic controllers.
No ferries will sail to the Greek islands and no trains will run.
The strike has been called by two powerful unions, the 600,000-member General Confederation of Greek workers (GSEE), and the Public Employees Federation (Adedy) which has 200,000 members.
They are demanding a change in policy, condemning privatizations being carried out, austerity over pay, higher taxes and pension reform.
Greeks face a news blackout as the journalists union is joining the strike, and courts will be closed in the absence of lawyers and officials.
Public transport in
Many schools will be shut. Banks, government offices and big publicly-owned enterprises such as the state electricity company will be hit.
The two unions are planning a rally and a march in the centre of