Airlines will be able to withstand the impact of Britain leaving the European Union, even without a deal, but the lack of political progress is frustrating and has dampened consumer demand, airline chiefs said today. 

Britain is due to leave the European Union on March 29, and Prime Minister Theresa May has yet to seal a deal that has the approval of lawmakers in Westminster.

"I don't think it's concern that we've expressed - it's frustration. We do really need the politicians to resolve this," Willie Walsh, CEO of British Airways and Aer Lingus parent IAG said.

He made his comments at the Airline for Europe summit in Brussels. 

"The industry manages (these uncertainties) better than any other industry. I'm fairly confident that IAG and other airlines will be able to manage this situation whatever happens," Mr Walsh said. 

Ryanair chief executive Michael O'Leary told Reuters that even if a deal is passed, it would only clinch a transition arrangement until the end of 2020, with further political instability delayed but not resolved. 

Ryanair CEO Michael O'Leary

"(A deal) is good news in the short term but fixes nothing over the medium term because they are still going to have to negotiate the trade deal. And what the UK government have demonstrated in the last two years is that they are incapable of negotiating the purchase of a packet of crisps," he said. 

"So short term I think the threat of a cliff edge is moving away but it is only going to be postponed for another 21 months and now we are back to the same situation all over again." 

Britain and the EU have said that flights will continue, even in the event that there is a no-deal Brexit. 

The EU has proposed a provisional arrangement to mitigate the impact of a no-deal Brexit on airlines, including an extra six months to meet rules requiring airlines flying within the single market to be majority-owned by shareholders from its countries. 

EasyJet chief executive Johan Lundgren told Reuters on the sidelines of the summit that those moves were reassuring the companies that they could operate, even if ongoing uncertainty was not good for consumers. 

"The uncertainty that exists around Brexit and the impact that this has on the customer is not helpful, is not good," he said. 

"(But) even in the event of a no-deal, we are prepared, because we know there will be a deal on aviation," he added.

Meanwhile, the IAG boss said the airline is unlikely to renew its interest in Norwegian Air after ruling out a new bid for the Scandinavian carrier earlier in the year.

"I'd never say never, but I think it's unlikely," Walsh told reporters on the sidelines of the Airlines for Europe summit in Brussels. 

IAG sold its stake in Norwegian when it ended its interest in the airline, which competes with IAG's low-cost long-haul Level brand, earlier this year. 

"If there was a case that we might have done that (renewed our interest), we probably would have retained the shares in Norwegian," he added. 

Asked if Level could expand into Scandinavia, Walsh said: "It could, ultimately." 

"There are several significant markets that are underserved from a long-haul point of view and can be best served by a low-cost model," he said.

He also said that, although he was still not interested in buying A380s, those who wanted to approach him with offers after Airbus said it was scrapping production of the superjumbo should do so. 

"I'm not looking to buy A380s. If there are people looking to sell them, they should probably approach us, because we would be one of the few people who might be interested. 

"But I'm not looking to buy," he said. "Let's see what happens."