London Heathrow Airport could be boosted by extra trade if Britain leaves the European Union without a deal and Britain's seaports and roads get clogged up with extra congestion, the airport's chief executive said. 

John Holland-Kaye, CEO of Heathrow said he was not hoping for a "no-deal" Brexit outcome but that the airport would be resilient to disruption if there was one. 

"In the short-term, if there are queues at Dover, then there may be more cargo going on short-haul planes from European markets," he told Reuters.

He said the airport, the biggest in Europe, had spent several million pounds preparing for no-deal. 

"We don't want to have a no-deal Brexit, and we don't see a commercial advantage in a no-deal Brexit, but we are prepared for no deal," he stated. 

Mr Holland-Kaye said the airport had begun stockpiling some items, such as mechanical components and rubber gloves, that come from the EU in case of disruption around Brexit. 

He said that the airport had been working on the assumption of a no-deal Brexit for the past four to five months. 

Planes will keep moving even in a no-deal scenario, Holland-Kaye said, adding that the EU had shown flexibility on issues such as caps for air traffic in recent weeks. 

"We've seen more pragmatism coming in from the EU side over the last month or so, as they've started to understand that these kind of constraints are not in the interests of their carriers," he said. 

Heathrow Airport, owned by Ferrovial, Qatar Investment Authority and China Investment Corporation among others, said a record 80.1 million customers had flown through the airport, with 3% revenue growth. 

Holland-Kaye said that plans for a new runway, due to open in 2026, were on track, after politicians voted to approve expansion last year.