Airports have warned travellers to expect disruption on arrival into the UK as immigration and customs officers join the public sector strike tomorrow.
Passengers have been advised to consider travelling on a different day to avoid delays as hundreds of staff walk out.
A spokeswoman for airport operator BAA, which runs Heathrow, Stansted, Edinburgh, Glasgow, Aberdeen and Southampton airports, said: "We have been informed by UK Border Agency that arriving passengers should expect delays at the UK border on Thursday as a result of industrial action by immigration officers.
"UK Border Agency are advising that passengers who can do so may wish to travel on other dates."
The UK Border Agency said queues were expected at many ports and airports, but stressed that maintaining security was its priority.
A spokeswoman for the agency added that the extent of the disruption would depend on how many staff decide to take part in the strike action, and at which locations. She said: "If queues do build up, we have contingency measures in place to manage them."
Airlines are also preparing for the impact of the strike action.
A British Airways spokeswoman said: "We are liaising closely with the UK Border Agency and airport owners to minimise potential inconvenience to our customers.
"This is clearly an issue beyond our control but we are doing everything we can to protect our customers."
A spokesman for easyJet said it was hoped that passengers departing the UK and those on domestic flights would avoid disruption, but warned they could also be hit as a knock-on effect.
He said: "The challenge will be if the immigration halls, which are small in some airports, start to overflow, which could cause more general problems.
"We are trying to minimise the impact and have asked airports to find spaces elsewhere for people to queue if the immigration halls do overflow."
The airline is advising its passengers to "continue to plan to fly", and added: "We are saying that if you are inbound, you may experience longer than normal queues to get through passport control. But we are putting our resources together and hope to minimise the impact on outbound passengers and those on UK domestic flights."
High-speed Channel Tunnel train company Eurostar said it would not be affected by industrial action.
It added that it was running two extra trains tomorrow - one from London to Paris, the other from Paris to London, to cope with expected extra demand.
Southampton airport said today it was not expecting disruption for passengers from strike action tomorrow.Reuse content