More than 500 planes flew from Norwich Airport with no passengers on board or less than 10pc full during part of the Covid pandemic, official figures revealed.

And today the number of so-called 'ghost flights' has been criticised by Green campaigners.

Parliamentary figures showed almost 15,000 flights departed the UK with no passengers, or less than 10pc capacity, between March 2020 and September last year.

Flights from Norwich accounted for 506 of them, but it remains unclear which airlines were affected.

There is a long-running system, where airlines have had to keep using airport ‘slots’ or risk losing them to rivals, which was suspended by the UK government during the pandemic.

Such a system does not operate at Norwich Airport - although it does at international airports which planes fly to.

KLM flies from Norwich to Amsterdam - where it has to fulfill a certain percentage of slots or risk losing them.

A KLM spokesperson said: "The European slot release rules are set at 50pc for the winter. This means you have to run half of your flights or you will lose those slots.

"So if the rest of the season is very disappointing, you as an airline could find yourself in a situation where you either lose slots because you cancel flights or fly with half-empty planes."

KLM says it has not operated its planes under the 10pc threshold.

A spokesperson for TUI said: "We can confirm all of our commercial flights from Norwich between March 2020 and September 2021 operated with more than 10pc of seats filled."

She said it was normal practice for charter airlines to operate 'positioning' flights which go out or return empty and a "very small" number had been flown.

A spokeswoman for Norwich Airport said it was a matter for the airlines.

Aviation minister Robert Courts said legislation will reduce airlines operating "environmentally damaging empty or near-empty flights".

But Green city councillor Denise Carlo warned: “Time is running out to stop dangerous climate change and yet we learn that Norwich Airport had a large number of near empty monthly flights during Covid.

"We cannot hope to stay within the safe level of 1.5C of warming unless businesses behave responsibly."

In 2008, Flybe admitted it paid actors to be passengers on flights from Norwich to Dublin, in an attempt to reach a quota and secure a bonus.