Heathrow has opened a dedicated red list arrivals facility at Terminal 3.
The aim is to create more capacity for arrivals when the government expands its green list of countries which do not require quarantine on return to the UK under the traffic light system.
A review of the list from June 7 is expected to be published later this week.
The dedicated facility in Terminal 3 opens today (Tuesday) before it is moved to Terminal 4.
More: Comment: Africa deserves better than the red list
Tui cancels holidays to Turkey and eight other countries
A total of 43 countries are on the red list with direct flights only allowed from a limited number of them. However, it is expected that further countries could be added.
Anyone who has been in a red list country in the previous ten days, whether they took a direct flight or came via another country, is required to pay for quarantine in a hotel for ten nights after their arrival.
But concerns have been raised about travellers from red list countries mixing with others queuing in airport immigration halls.
A Heathrow spokeswoman said: “Red list routes will likely be a feature of UK travel for the foreseeable future as countries vaccinate their populations at different rates.
“We’re adapting Heathrow to this longer-term reality by initially opening a dedicated arrivals facility.”
She told the BBC that while opening the facility would be “logistically very challenging”, Heathrow hoped that doing so would enable Border Force to carry out its duties more efficiently, as passenger volumes increase in line with countries on the government’s green list.
The new measure was introduced as Heathrow warned that the UK is set to miss out on billions of pounds of passenger spend if the green list is not extended as part of the travel review on June 7.
New research from economic forecasting group CEBR found that passengers arriving at Heathrow alone spend more than £16 billion across the country.
US visitors travelling through Heathrow are the largest source of inbound tourism revenue for the entire economy, accounting for £3.74 billion, nearly a quarter (23%) of total spend while visiting the UK.
The US was the top market for passenger traffic prior to the pandemic, with Heathrow–New York JFK one of the world’s most lucrative routes.
More than 21 million passengers travelled from the airport to the US in 2019.
The study also indicated that expenditure by passengers using Heathrow is set to grow to £18.1 billion a year by the middle of the decade, if international air travel resumes this summer.
But if conditions prevent that and visitor numbers grow more slowly, expenditure could fall by more than 18% to £13.6 billion by 2025.
Visits to the UK in 2020 were 73% down on pre-pandemic levels, according to recently published Office for National Statistics data, causing total visitor spend to drop by 78% from 2019 levels to just £6.2 billion.
Heathrow argues that rapid progress has been made with the global vaccine rollout since the initial restart of international travel on May 17, especially in the US where the vaccination rate is fast catching up to UK levels.
The airport said: “This progress, alongside testing and the government’s own risk-based controls, allows for links to be safely restored to more of the UK’s low risk key trading partners, unleashing the huge economic contribution of these visitors, while protecting the gains made in the fight against this virus.”
Heathrow chief executive John Holland-Kaye said: “This research shows just how many businesses across the UK are losing out because of the government’s restrictions on access to overseas visitors and markets.
“The government has the tools to protect both public health and the economy and ministers must unlock more low risk destinations across Europe, as well as the US, as part of the next review on June 7.”