Airlines have operated more than 14,000 so-called ghost flights from UK airports during the coronavirus pandemic, new figures show.

The international flights, which had no more than 10% of their seats filled, departed from 32 airports between March 2020 and September 2021, according to Government analysis.

Heathrow had the most with 4,910 flights, followed by Manchester (1,548 flights) and Gatwick (1,044 flights).

A total of 14,472 empty or nearly empty flights were recorded over the 19-month period, at an average of 25 every day.

The figures include flights which were operated mainly to transport cargo or repatriate Britons stranded overseas.

Airlines have traditionally run ghost flights when they need to hit the 80% threshold for using valuable take-off and landing slots at congested airports to retain the right to use them during the following year.

This has led to concern about the environmental impact of the flights.

But slot rules have been eased during the virus crisis due to the lack of demand for travel.

Aviation minister Roberts Courts, who published the analysis of Civil Aviation Authority data in response to a parliamentary question, said: “Departing flights may operate with a low number of passengers for a range of reasons.

“Since the onset of the pandemic, the Government has provided alleviation from the normal slot regulations that require airlines to operate 80% of their slots in order to retain them for the following season.

“This means that airlines have not been required to operate empty or almost empty flights solely to retain their historic slots rights.”

Heathrow chief executive John Holland-Kaye said flights with low passenger numbers were often used to transport cargo.

He told the PA news agency: “If you were flying PPE (personal protective equipment) from China or UK exports into the US while those markets were closed (to leisure travel), you would fly them on a passenger plane and you might only have a couple of passengers on board.”

He added: “Given how tight finances are, nobody is flying a plane unless it is economically viable. This is actually about keeping the UK supply chain going while borders are closed for passengers.”

British Airways and Virgin Atlantic insisted they have not operated “ghost flights” to retain slots during the pandemic.

A Virgin Atlantic spokeswoman said its low-occupancy flights “supported the global movement of people including returning foreign citizens and repatriated UK citizens, as well as keeping global supply chains running by moving vital cargo, including medical supplies and PPE”.

Slot rules were suspended at UK airports shortly after the start of the pandemic but were reintroduced at 50% in October 2021.

The Department for Transport (DfT) is ramping this up to 70% next month.

The Virgin Atlantic spokeswoman said it is “disappointing” that the DfT has “set the highest slot use threshold in the world for the summer 2022 season”.

She continued: “This decision risks setting back the aviation industry and UK economic recovery during a crucial phase, and could lead to inefficient flying by some carriers simply to maintain airport slots, with markets in Asia still up to 90% below 2019 demand levels, including greater China which is largely closed to foreign visitors.”