Until March, Gatwick was the busiest single-runway airport in the world. Today, the Sussex hub, code LGW, is open for just eight hours a day – and it may be about to lose its second-biggest airline.

British Airways says it may never reopen its base at Gatwick airport.

In a letter to the Unite union seen by The Independent, BA’s managing director Gatwick, Adam Carson, wrote: “There is a possibility that we will look to close our full LGW operation.”

He told the union: “There is little prospect of early recovery even after the immediate health crisis subsides.

”We are now at a critical juncture and must table proposals for structural change so that our business is in a credible position to respond to what will be a challenging and uncertain trading environment for a sustained period of time.”

British Airways temporarily closed its Gatwick operation at the end of March as the coronavirus pandemic triggered a shutdown of aviation.

BA still has almost 1,900 cabin crew, including 352 customer service managers, who are furloughed under the government’s job retention scheme.

British Airways has a majority of slots at Heathrow, its main base, and intends to consolidate most or all of its operation there. If the airline decides not to resume operations at Gatwick, a few staff may find work at Heathrow.

Even if BA decides to retain a smaller presence at the Sussex airport – which it has served for 46 years – most employees will be made redundant.

As a minimum, British Airways intends to cut four out of five of senior cabin crew from the workforce. Junior posts would be reduced by 57 per cent. Ground staff, numbering more than 300, would be transferred to Gatwick Ground Services, a separate company.

BA’s letter to the union said: “These proposals are at a very early stage.” But the airline expects to make redundancies between mid-June and the end of 2020.

Staff who lose their jobs can expect only a bare minimum of compensation.

The airline said: “The cost of delivering any enhanced voluntary redundancy programme will now be prohibitively expensive.”

British Airways announced airline-wide job cuts affecting 12,000 of the 42,000 staff on Wednesday, in a process called “Preparing for a Different Future”.

The letter claimed that subsidies to rivals were a factor, saying: “Many of British Airways’ competitors in Europe and globally are receiving state aid in various forms.

“The resulting competitive environment will create a distorted market where some of those competitors will have the option to provide overcapacity and lower fares.

“We consider that these changes would allow us to have a competitive and sustainable employee cost base, which would meet demand.”

The airline has been a significant presence at Gatwick ever since British Airways was created in 1974. BA expanded substantially when it took over British Caledonian in 1987, and added additional capacity by buying Dan Air for a token £1 in 1992.

British Airways currently serves a wide range of European and long-haul destinations, with a leisure focus – as opposed to the business profile at Heathrow. Key destinations include many Mediterranean cities, Florida and the Caribbean.

Passengers with bookings on British Airways from Gatwick can only wait to be told if their flights will go ahead. If they are cancelled, BA is obliged to provide alternative services – possibly from Heathrow, or on other airlines such as easyJet or Virgin Atlantic from Gatwick.

Whether or not BA retains some sort of presence at the Sussex airport, a large number of previously precious “slots” will be freed up.

One possibility is that Vueling, sister airline to British Airways in the IAG conglomerate, will move in at scale and use a significant number of the landing and take-off permits at Gatwick.

The biggest carrier at Gatwick, easyJet, may wish to expand to fill the vacuum. But another player such as Jet2 of Leeds could establish a base at the Sussex airport.