Good Friday is expected to be the busiest day for Brits travelling overseas for Easter, after Thursday saw long delays on the nation's roads.
Travel trade organisation Abta estimates that two million Brits will head overseas during Easter, with Spain and Portugal among the most popular destinations.
But holidaymakers heading to Portugal have been warned to expect delays at the country's airports due to a strike by security guards.
EasyJet said passengers should expect longer security queues until Monday due to the industrial action, while British Airways expects the departures area of Lisbon Airport to be "particularly affected" by the strike.
An EasyJet spokesman said: "We strongly recommend that you allow extra time for your journey through the airport to be able to get to the gate on time."
The Foreign and Commonwealth Office advised travellers to Portugal to check-in luggage to reduce the number of bags requiring screening.
All UK airports will be busy across the weekend, with 425,000 passengers jetting off from Heathrow, 250,000 from Gatwick, 153,000 from Stansted and 150,000 from Manchester.
Cross-Channel rail operator Eurostar is expecting its busiest ever Easter weekend, with 163,000 passengers making journeys, up 12% on last year.
Thursday saw a 17-mile jam on the M25 in Surrey after a car overturned and more than 20 million cars are set to be on the roads between Thursday and Monday.
The worst times to travel were expected to be between 10am and 2pm on Good Friday and 10am and 5pm on Easter Monday.
Abta chief executive Mark Tanzer said: "Whilst many families may have already begun their Easter break, the Easter weekend is always a busy time of year for the travel industry with many holidaymakers taking advantage of the bank holidays to grab some much-needed sunshine or a trip to one of the world's great cities.
"The roads will be busy, so we would recommend leaving a little extra time to get to your port of departure and if using public transport, to check in advance for engineering works."