Carmakers and airlines easyJet and Ryanair demanded Britain secure a Brexit deal which preserves their access to Europe, warning any barriers to trade could risk the future of car plants and ground flights between the UK and the continent.
No deal in Brexit talks is not an option, Britain's car industry body said on Wednesday after Theresa May formally launched divorce proceedings from the European Union, saying tariffs would raise costs and hit consumers.
Ford, Britain's biggest automotive engine-maker and Rolls-Royce and Mini-maker BMW both warned that unfettered access to the European Union remained crucial.
"Any deal must include securing tariff-free trade with the wider Customs Union and not just the EU27, whilst retaining access to the best talent and resources," Ford of Europe president Jim Farley said.
"It also is critical that a transitional period is put in place to ensure that customers are not penalized and to maintain free trade."
Ford builds vans in Turkey, which is not part of the EU but is in the EU customs union, whilst BMW builds its Mini cars at a central English plant in Oxford and is due to decide by the end of the year where to build its electric models.
Irish airline Ryanair said flights between Britain and the European Union risk being suspended in 2019 if Britain does not prioritize a new aviation deal whilst rival easyJet said it wanted a straightforward bilateral aviation agreement.
"There is a distinct possibility that there may be no flights between the UK and Europe for a period of time after March 2019," Ryanair's chief marketing officer Kenny Jacobs said on Wednesday.
Most international firms which publicly expressed an opinion ahead of last June's referendum backed Britain remaining in the European Union, fearful of extra costs, trade barriers and unpredictable currency swings.
May has said she will take Britain out of the European single market but will seek the best possible access to the European markets and establish better trade ties with other nations.
But airlines are among those concerned that trading conditions vital to their operations could be lost.
Britain will have to renegotiate access to the single aviation market, whereby airlines based in the EU have the right to fly to and from any country in the bloc or even within other member states.
German media conglomerate Bertelsmann said on Tuesday it may have to reconsider London as the base for its intellectual property operations.
"We have made an impact analysis," Chief Executive Thomas Rabe said.
"In about a year's time we will have to come to a decision, when the impact of the Brexit will become more clear."