UK airports are warning of delays for arriving passengers because they lack the technology to handle COVID-19 forms.
Ahead of the country's 'traffic light' system opening up air travel this week, the industry says manual checks of the passenger locator forms risk creating "unacceptable" queues at the border.
Airport managers have appealed to the government for digital technology to speed up the process.
The PLF is a form which includes a passenger's COVID test history and where they will be staying in the UK. It can be completed online but needs to be checked upon arrival, manually, by UK border staff.
London Heathrow and Edinburgh Airport have both warned of passenger bottlenecks and say the UK government needs to digitise the PLF to make it readable by unmanned, automated 'e-gates', which already read passports without the need for inspection by staff.
Gordon Dewar, chief executive of Edinburgh Airport, told Sky News that 70% of international arrivals in the city are typically processed through 'e-gates', but that the PLF currently needs a manual check by UK border staff which will multiply passenger processing time.
"A typical European arrival would be a 20-30 seconds 'transaction', in which there's nothing complicated except a scan of the passport and that's checked against the database.
"But now we've got passenger locator forms - and we're not challenging that, they are sensible - but relying on a people system is just going to add enormously to the time. Every transaction is going to take three or four times longer."
"Clearly, that's not good for the customer experience and is actually quite a worry in terms of being able to socially distance and make sure people are as safe as they can be. If we could find a digital version, we could minimise queues."
A spokesperson for Heathrow Airport said: "In order to ensure passengers are not left to queue for unacceptable lengths of time on arrival, government must deliver on the automation of the passenger locator form to allow e-gates to re-open and Border Force must man every desk to prevent bottlenecks from forming at the border."
From Monday, international travel is allowed to and from the UK, governed by a 'traffic light' system. Health checks upon arrival in the country will vary according to whether a journey started in a country on a red, amber or green list.
An upgrade of automated e-gates is due to be completed in the autumn of this year.
A Home Office spokesperson said: "Protecting public health is our priority and as we reopen international travel safely we will maintain 100% health checks at the border to protect the wider public and our vaccine rollout.
"While we do this, wait times are likely to be longer and we will do all we can to smooth the process, including the roll-out of our e-gate upgrade programme during the summer and deploying additional Border Force officers."