Former Tui joint chief executive Peter Long and easyJet chief executive Carolyn McCall both made separate warnings in yesterday’s Sunday Times.

Long stated that the pan European response to last year’s terrorist attack on a beach in Tunisia which killed 38, 33 of whom were Tui customers, was a crucial part of “looking after and ensuring the safety of our customers”.

He also told the paper that it would be a threat to security if European countries did not “work together to deal with these crises”.

Long added: “I am very happy that when we are looking at security we can see all the foreign ministries are aligned. That’s only helpful in terms of us ensuring we protect the security of our travellers.”

He also argued the creation of Tui as it is now following the merger with First Choice in 2007 was only made possible by the fact that Britain is in the EU.

“I do not believe that we would have created a pan-European company had we not been in Europe,” Long said.

“The complexities of two cross-border mergers would not have happened.”

He also warned of the impact Brexit would have on the cost of a holiday, arguing they would become more expensive after the pound takes a hammering in the wake of any departure.

McCall agreed that leaving the EU would have a negative impact on the cost of travelling for Brits.

In a column for the Sunday newspaper she wrote: “The European debate is vital both to airlines and their passengers. As a result of Britain’s membership, the costs of flights have plummeted while the range of destinations has soared.

“That’s why easyJet believes the benefits far outweigh the frustrations – and why the UK is better off as part of the EU.

“Think back to the time before the EU created the common aviation area in the 1990s. Few people flew; it was something reserved for the elite.

“Those who did fly found themselves travelling on government-owned airlines between state-controlled airports.

“Those governments decided how many airlines flew – usually just one flag carrier from each country – and the number of flights.

“They also dictated the fares, which were often prohibitively expensive. It seemed that any flight anywhere in Europe cost at least £250, and singles were as costly as returns.

“Then came the revolution in air travel. Britain led the way in this liberalisation, but it was the EU that gave airlines the freedom to fly across the continent.

“That led to a dramatic fall in fares – around a 40% cut – and the number of routes increasing by 180%. The number of people who flew to and from the UK was 101m in 1995. By 2014 it had almost doubled to 199m.

“EasyJet was born from this deregulation, which helped travellers of all ages and incomes to reach destinations they could previously only have dreamed of.

“It’s not just about the flights; it’s what they enable people to do – to live, work and holiday in the world’s biggest economic bloc and most culturally diverse continent.

“The growth in mobility has encouraged trade, supported the movement of skills into the UK economy and, of course, enabled people to travel.

McCall added UK travel and tourism is now worth £170 billion, accounting for more than 10% of the economy, while four million jobs are either directly or indirectly supported by the business.

She also said: “The EU is not perfect and it does need reform. We support the efforts of the prime minister in improving the terms of our relationship.

“But remaining within the EU means that the UK can directly influence the rules governing the single market – rules that affect our industry and our passengers.

“Look at just one current example. EasyJet has come together with Europe’s largest airlines to form a new association, Airlines for Europe, to work with Brussels and push for the regulatory changes that we need in order to grow, deliver jobs and provide the best services for our consumers.

“That requires smarter regulation of the parts of our industry still dominated by monopoly suppliers, such as the larger airports.

“Passenger charges at Europe’s 10 largest airports have increased by around four times the rate of inflation in the last decade. We want that to change.

“More active EU intervention in this area will reduce fares for passengers, just as the EU helped consumers by reducing mobile phone roaming charges.

“How much you pay for your holiday really does depend on how much influence Britain has in Europe.

“The EU has brought other benefits. Consumer rights guarantee that passengers are provided a hotel room if their flight is cancelled, and legislation ensures that passengers with reduced mobility are properly cared for wherever they fly in Europe. Both initiatives came from Brussels.

“Whichever European airline you fly on, it operates to the same safety standards as easyJet, with unsafe airlines being banned from European skies. That also came from Brussels.”