Photographs have emerged showing large queues at the Eurostar terminal in Paris and Manchester airport as many return from the bank holiday.
The AA warned the roads will be especially busy as people head home ahead of the working week.
At least 20 flights between London and Scotland have been cancelled by British Airways and easyJet, as well as Heathrow-bound flights from European cities such as Paris, Amsterdam and Geneva.
It comes as large queues at airports over recent weeks has prompted ministers to relax counterterrorism checks for new staff so they can start working faster.
New starters will be trained without security vetting but will not be able to work with airside access to the planes and runways.
Airports across the country have been hit with staff shortages due and there have been delays at Heathrow, Gatwick, Birmingham and Manchester.
Immigration Services Union general secretary Lucy Moreton said: “This weekend, catastrophically understaffed, with people travelling again, we anticipate queues will move from security-based queues going outward to Border Force queues coming back in.”
Meanwhile, travel bosses said rail engineering works would lead to more people travelling via car.
RAC spokesman Simon Williams said: “Rail engineering works lead to more road congestion as some people travel by car instead.”
Meanwhile, AA spokesperson Tony Rich said more people will be travelling over the holiday after many missed out on occasions during Christmas due to Covid.
He said: “People’s desire to travel is making this Easter a bit like Christmas, with people seeing friends and family after not seeing them very much during Covid.
“Our survey shows people want to make the most of the holiday weekend. It shows the demand to do what we have missed during the past two years.
“The weather is a factor, and encourages more travel, and people’s determination to go on trips outweighs concern over fuel costs.”
Around 500 replacement bus journeys have been put on over Easter.
West Coast Line works are seeing coaches used as almost 50 miles of the route is shut between London Euston and Milton Keynes.
Every Stansted Express rail traveller is being ferried by bus to and from the airport.
Richard Freeston-Clough, spokesman for passenger watchdog London TravelWatch, said: “More leisure rail journeys are taking place as it is Easter - but engineering projects mean disruption.”
A Network Rail spokesman said the vast majority of the network is open for business as usual.
“Where our projects are hitting services, we aim to keep disruption to a minimum by using alternative routes and using of buses as the last resort,” the spokesman added.