The Ryanair boss, Michael O’Leary, has pledged to back David Cameron’s campaign to keep Britain in a reformed Europe, saying it made the UK better off, as the Irish airline announced soaring half-yearly profits of more than €1bn.

The airline, Europe’s biggest by passenger numbers, increased its pre-tax profit for the six months to the end of September by 37% to €1.09bn (£780m) after a bumper summer. O’Leary said a strong pound and bad weather in northern Europe had encouraged more people to fly to warmer climes, with a 13% jump in passengers filling Ryanair’s planes. Cheaper fuel cut the airline’s costs by 6% from a year ago.

O’Leary said Ryanair would continue to expand in Europe and that his airline would be urging British voters to stay in the EU. “We will be very actively supporting a yes vote in the referendum. There is absolutely no doubt that the UK economy is better off in Europe than outside,” he said.

The prime minister has promised a referendum on Britain’s EU membership by the end of 2017, and is attempting to persuade other states to renegotiate terms. O’Leary said: “We need a reformed Europe with some sensible voices around the table or we are all at the mercy of the French and the Germans. The UK is a very sensible and effective counterbalance to the regulation that comes out of Brussels.

“I’d like to see a lot less regulation and a lot more freedom of movement of goods, capital and labour. We should be free to create more jobs and not have artificial restrictions.”

The airline has had frequent run-ins over the employment status of crew in bases around Europe, and O’Leary has called for a ban on strikes by air traffic controllers. While Ryanair has improved its image with customers, its hardline approach to trade unions and workers’ rights has persisted. It closed its Danish bases after a bruising row with unions and Copenhagen’s mayor accused it of “social dumping” because of low wages.

However, O’Leary said Ryanair was “going gangbusters” in Copenhagen, doubling the number of flights and customers served. He said: “Apparently industrial relations terrorism is now legal in Denmark. So we’ve shipped our aircraft out of Denmark and we fly in from London, Dublin and Kaunas … but they can’t blockade us because we don’t employ people there.”

He said long-haul Ryanair flights were now “off the table, off the radar”. However, he confirmed that the airline had held talks to provide short-haul connections into other airlines’ long-haul services – including Aer Lingus in Dublin, TAP in Lisbon, and Norwegian and Virgin at Gatwick. “It will be a small part of our business but it’s an inevitable development,” he said.

But he ruled out codesharing – where airlines can market each other’s flights – saying Ryanair had told the full-service carriers: “We don’t want any of that cumbersome, complicated crap. You look after the passenger, it’s your responsibility … Life is too short for the complexities.”

Ryanair has partially transformed its uncompromising image by scrapping some charges and restrictions, improving customer service and revamping the company website. O’Leary said the next venture would be to host price comparisons on his website to “drive Skyscanner out of business”. He said he was attempting to persuade other airlines – notably easyJet – to sign up, without success: “I’m full, I don’t need your passengers. We would spill to each other, to more expensive airlines. But it makes no sense for us, because of our refusal to work together, to create a business for SkyScanner or the pirates of eNightmares [eDreams].”

Ryanair expects to fly 105 million passengers this year, rising to 180 million by 2024 – 20 million more than previously forecast. O’Leary said hedging activity would also bring fuel savings of €430m by 2017. “Most airlines in Europe next year are going to look like management geniuses. You’ve only lowered your costs because your fuel bills fell,” he said.

Ryanair is pushing into Germany and O’Leary said he expected Lufthansa, the German flag carrier, to cut prices. “If anyone wants to have a price war in our markets, just let us know. We will be happy to meet you,” he said.