All ferry ports in Greece will be closed today due to a national strike, which could also hit flights.
The Foreign Office is warning Britons travelling to Greece that some flights within the country might be affected.
It said those planning to travel on November 12 should contact their airline, tour operator or ferry company for advice.
EasyJet said it had been advised of planned industrial action by Greek air traffic controllers.
"Like all airlines, our flights to and from Greek airports might be affected," it said.
"We plan to operate our normal schedule, but expect delays to our flights throughout the day."
