Easter travellers could face delays at airports, train stations and ports as security has been stepped up, the Government is warning.
Security was beefed up after the atrocities in Brussels and will disrupt journeys.
An estimated two million people are expected to travel abroad over the long weekend, with millions more passing through domestic transport hubs.
Travel organisation Abta estimates that two million Britons will go abroad over the four-day weekend.
It urged travellers to allow "adequate time" for extra security checks.
Eurostar is advising passengers to allow up to an hour for check in due to increased security checks.
More than 22,000 passengers are expected to use Eurostar services on Good Friday.