Writing in the Sunday Times, McCall said: "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."
According to the Press Association, Peter Long, former boss of TUI, also says that close cooperation with other EU states is essential to "protect the security of our holidaymakers".
When dozens of holidaymakers were killed in the Tunisia terror attack last year, he says it gave him "many first-hand experiences of seeing how European governments, through their foreign offices, collaborate and work together in a crisis".
Long added that Brexit would cause the value of the pound to slump, pushing up the cost of holidays.
Top travel hacks for cheaper holidays
Brexit would mean the end of cheap flights and holidays, says Easyjet chief
Flight systems are loaded first thing every morning so flights which were on hold overnight (usually from business customers) will be released. This happens at around 1am, so you can often get better prices the earlier you book – a hack four in five Brits have never heard of.
Starting your long haul holiday from another European city can save you lots of money. You can extend your holiday by visiting interesting European cities and bag a bargain by starting your trip, for example, in Sofia or Oslo. You only need to add a low-cost flight from your home to the city to take advantage of amazing discounts and offers. For example, you can bag a return flight from Sofia, Bulgaria to Dubai for under £150.
The best days to fly are Tuesday to Thursday so you avoid the Monday morning rush of business travellers and also the weekend escapers. These dates often have better availability too and the best availability means low fares!
Many European cities have set days during the year when they open up their top museums at night and offer free access. The European Night of Museums in France, Germany and the UK is in May, while Budapest and Prague offer the same thing in June.
The major airlines all have seat sales over the Christmas period, so this is the perfect time to book your next break at a great price. During Black Friday (at the end of November) and over Christmas, lastminute.com, for example, offers access to these big sales of the airlines with amazing flight deals.
Many cities that are popular for business travellers, such as London, Brussels and Zurich, have fantastic room rates at the weekend once the 'suits' have left. You can sometimes find five-star hotels for under £100 per night.
Hotels want to keep you there for every meal of the day if possible, so ask when you check in if they offer a discount on breakfast or dinner for guests of the hotel. Free 'welcome' drinks are also common to get you into the bar or restaurant.
The cheapest time of year for a city break is January, with deals for flights and a hotel stay for two nights available under £100 in places like Berlin, Dublin, Prague and Copenhagen.
Sunday nights are usually the cheapest night of the week to stay in a city hotel. This is the end of the week when weekend travellers have left and before corporate guests arrive so a great day to surprise your other half with a night away. You’re also more likely to bag an upgrade to a suite when the hotel is quieter on a Sunday.
If you don't want to wait for your food on the plane order special meals in advance – like vegetarian or low calorie. These get delivered to seats first so you’re guaranteed a hot dinner before most other passengers.