Earlier this week, Heathrow’s chief solutions officer, Chris Garton, told the government’s transport committee the queues at the airport caused by additional Covid-19 checks at the border were becoming "untenable".

Garton said, on occasion, police had to be involved, and stressed the problem would become significantly worse if the government does lift restrictions on international travel from 17 May.

Despite just 10,000 to 15,000 people currently arriving at the airport, Britain’s busiest, every day, more than half were currently having to queue for in excess of two to three hours.

Iata has called on the UK government to accelerate efforts to "digitalise" the current paper-based system for proof of testing results and any Covid-19 vaccine certification.

"When international travel ramps up from 17 May, it’s critical that passengers are not left queuing for hours for the manual checking of vaccine and testing certificates," said Iata.

"Even with limited traffic, there are already reports of lengthy waits at UK border checkpoints. This compromises social distancing measures and passenger welfare."

Iata highlighted how the government, in the report of its Global Travel Taskforce, has set out its intention to work with industry on digital systems, such as Iata’s own travel pass, to manage testing and vaccination documentation, something it said it welcomed – while warning there was still "a lot of work to do" before 17 May.

"With just over a month to go, it is urgent that agreement is reached on what digital systems will be accepted, trials are conducted to ensure their smooth implementation, and communication programs reach travellers who will need to arrive at the airport prepared," said Iata. "There is no time to lose."