Eurostar trains are among the services in growing demand
Travel firms have seen bookings surge as people seek different travel arrangements after planes were grounded in the UK because of volcanic ash.
Eurostar said some of Thursday's services between the UK and mainland Europe were almost full after "thousands" of extra reservations.
Virgin Trains said it was carrying an extra 2,000 passengers between Glasgow and London.
Ferry companies also reported an increase in enquiries.
A spokesman for Brittany Ferries said people were hastily re-arranging travel plans.
"We expect Spain routes to be particularly busy, given that it is the biggest tourist destination for Britons," he added.
Passengers also appeared to be altering travel arrangements for Friday and the weekend - anticipating further disruption.
Eurostar said many of its Friday trains, which were already busy due to demand for spring breaks, were filling up.
And a spokesman for P&O ferries said passengers were "not going to risk any prolonged closure of airports" so were booking ahead.
The grounding of aircraft would cause some short term impact on productivity in the UK as some people were unable to get to work according to the Centre for Economic and Business Research (CEBR).
However the ability for people to work form home , and the tendency to make up lost time later meant it would probably have only a limited impact.
Many businesses have been assessing the impact of planes being grounded:
• Freight being transported by air may suffer service delays, said FedEx, one of the world's largest transportation companies. It said operational contingency plans had been put in place and that shipments were being "routed to non-affected airports" where possible
• Courier companies TNT and DHL also said their operations had been impacted. TNT said some deliveries were subject to delays of up to 24 hours, adding that it was switching some parcels from air to road deliveries to cope with the situation
• Tourism body VisitBritain said hotels were not seeing much of a net loss because although tourists cannot get to the UK, some are stuck and are having to stay for longer
• Supermarkets said they were not seeing any difficulties. Waitrose said: "We are coming into the UK season so always source from the UK where we can." But it added that flowers from Kenya are being flown to the Netherlands and then being transported by road.
The Association of British Insurers (ABI) is advising customers to check their travel insurance policy, and speak to their travel insurer if they need clarification.
"Anyone who is likely to be affected should contact the airline or airport they are travelling from for the most up-to-date travel information," an ABI spokesperson said.
Meanwhile, the insurer Fortis said: "Fortis will be treating the volcanic ash incident as a bad weather event which means that customers may be entitled to claim under the terms of their travel insurance policy.
"Customers are advised to check their terms and conditions."
All flights in and out of the UK have been suspended as ash from a volcanic eruption in Iceland moves south. Airspace is also closed in Norway, Sweden, Finland and Denmark among other countries.
Safety body Eurocontrol said up to 4,000 flights across northern Europe had so far been affected by the cloud.
The Air Traffic Control Service (Nats) said restrictions on UK airspace will stay in place until 1900 BST on Friday amid fears of engine damage.
But flights from Northern Ireland and the Western Isles of Scotland to and from Glasgow, Edinburgh and Prestwick may be allowed from 0100 BST.
North Atlantic traffic to and from Edinburgh, Glasgow, Prestwick and Belfast may also be allowed.
Nats is due to give its next update after a review at 0830 BST.
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