Brexit - if Britain left the European Union - could see the end of cheap flights and a threat to travellers' safety, claim travel industry leaders.
EasyJet boss Carolyn McCall said how much people pay for their holiday really depends on how much influence Britain has in the EU.
She added that if Britain leaves the EU, cheap flights could be a thing of the past and flying could return to the days when it was 'reserved for the elite'.
While Peter Long, former boss of the TUI, said staying in the EU was essential to 'protect the security of holidaymakers'.
Writing in today's Sunday Times, Dame Carolyn McCall said: "The EU has brought huge benefits for UK travellers and businesses. Staying in the EU will ensure that they, and all of us, continue to receive them."
Mr Long said witnessing events following the Tunisia attacks had given him 'many first-hand experiences of seeing how European governments, through their foreign offices, collaborate and work together in a crisis'.
He added: "It would not be like that if we weren't in a situation where we were as Europe working together."
The comments come as a survey of 700 businesses found that 29% of British and German companies polled said they would either reduce capacities in the UK or relocate altogether in the event of a Brexit.
Businesses in the IT and technology sector are particularly open to upping sticks after a referendum: 41 per cent say they would consider decreasing capacity or relocating, according to the Bertelsmann Foundation's survey.