The European Union has been accused of damaging the environment by forcing airlines to operate tens of thousands of “ghost flights” just to keep their airport landing slots.

The Lufthansa Group, which includes Brussels Airlines, Austrian Airlines, Eurowings and Swiss, will have made a total of 18,000 unnecessary flights from mid-December to mid-March to comply with Brussels’ rules, according to the company.

Some 3,000 will be made by Brussels Airlines alone, prompting the Belgian government to urge the EU to rethink its rules on securing slots.

George Gilkinet, Belgium’s mobility minister, called for Brussels to put an end to this “environmental, economic and social nonsense” after it emerged his country’s national flag carrier was being forced to make so many empty flights.

Before the coronavirus pandemic hit, airlines had to fill at least 80 per cent of their scheduled take-off and landing slots, or risk losing them.

The European Commission has since revised that figure down to 50 per cent, but this still remains much higher than the actual number of flights needed to meet current passenger demand. Lufthansa has said it plans to cancel 33,000 scheduled flights by the end of March because of a slump in demand driven by the wave of omicron infections across the continent.

Boris Ogurksy, a Lufthansa spokesman, said: “Other regions of the world are taking a more pragmatic approach here, for example [in the US] by temporarily suspending slot rules due the current pandemic situation. That benefits the climate and the airlines.”

Environmentalists have also urged the EU to relax the rules to stop many of these empty flights taking to the skies.

Greta Thunberg sarcastically tweeted: “The EU surely is in a climate emergency mode.”

Greenpeace called the empty flights “absurd” and pointed to “a new low for the sector that is kept afloat with government support”.

Carsten Spohr, the airline group’s CEO, has previously described many of the 18,000 trips as “empty, unnecessary” flights.

Stay Grounded, a campaign group, said operating empty planes was an example of “bull**** flights”.

“It seems like the fact that we’re in a severe climate crisis and that flights are the fastest way to fry the planet has not arrived in the heads of decision makers and airlines,” the group said.

“If it had, empty flights would not be allowed anymore.”

A spokesman for the Commission said it “expects that operated flights follow consumer demand and offer much needed continued air connectivity to citizens”.

Britain has suspended its own rules of landing slots and isn’t expected to reintroduce them until the summer. 

A Belgian Department for Transport spokesman said: “Since the onset of the pandemic we have provided relief from the slots usage rule to mitigate financial harm to the sector and prevent environmentally damaging ghost flights.   

“Our aim is to support the sector’s recovery and we will announce our approach for summer 2022 shortly.”