Virgin founder and billionaire Richard Branson has thrown his support behind Britain remaining in the EU when the country votes in the June 23 referendum.

Speaking at a press conference to unveil a new generation of trains in London on Friday, Branson said it would be “the saddest day” if the UK voted in favour of a Brexit.

The 65-year-old said leaving the EU would Britain to “unfriendly” times, The Guardian reports.

Branson’s main fear is for the fate of budget airlines which make most of their money from European connections. He said:

“It’s quite likely that massive numbers of routes will be taken away from easyJet or Ryanair if we exit. The only reason they are allowed to fly in Europe is because we are part of it. I couldn’t see why the EU would be nice to us if we leave. Personally if I was in [the EU’s] shoes I’d want to punish people who desert the ship.”

Suggesting that the EU provided a fertile economy for European flights, the Virgin Atlantic owner said he hoped “sense” would prevail, adding that leaving would only make things more complicated for the UK.

“I think it would be one of the saddest days for Great Britain and the British people. A lot of the European nasties have already been sorted out. People talk about bureaucracy. The bureaucracy of all the things we’d have to do if we get out, dealing with all the tax we pay when we export products, that alone will will outweigh the cost of Europe to Britain.”

Most financial analysts think Britain leaving the EU would have a negative impact on its economy, though many admit they have no idea what a post-Brexit UK business environment would really look like.

Barclays released a report on Wednesday discussing the impact of a potential Brexit on the airline industry, and said it all came down to the impact on the greater economy:

In general, we think business travel demand is more geared on GDP than leisure. Therefore, should a potential EU exit negatively impact the economy, we think it could affect IAG [International Airline Groups] as much as easyJet, given British Airways’ exposure to corporate travel flows.

It concluded that airlines’ share prices would reflect this uncertainty June 23 draws closer.

Virgin Airlines does not actually fly to EU locations outside of the UK, but Branson’s comments reflect a broader concern over Brexit from many business leaders who believe Britain’s economy will be irrevocably harmed by leaving the trading bloc.

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