In Europe, airlines are operating 500 'ghost' flights a month to keep their airport landing slots. Critics call the requirement 'unnecessary'.

• Data obtained by The Guardian reveals that 500 "ghost" flights per month departed the UK from October to December.
• The flights are part of Europe's airport slot rule that requires airlines to fly 50% of allotted slots or lose them.

New data reveals that about 500 "ghost" flights per month flew in the UK in the fourth quarter of 2021, burning thousands of extra gallons of fuel and angering climate activists.

During the early onset of COVID-19, hundreds of "ghost" flights, which are empty or nearly empty planes, took to the skies so airlines could uphold Europe's "use it or lose it" airport slot rule. The policy requires carriers to operate 80% of their allocated takeoff and landing times or risk losing them to competitors.

The 80/20 rule, as it is called, was in effect at the very beginning of the pandemic, but the European Commission suspended the policy in mid-March 2020. This allowed airlines to avoid unnecessary flying to simply keep their airport slots.

However, the suspension ended in October and was reinstated as a 50% requirement instead of 80%, and, as a result, empty planes started flying once again.

According to data obtained by The Guardian via a freedom of information request to the UK's aviation regulator, from October to December, about 500 ghost flights per month flew in the UK.

The Guardian disclosed that the information only included flights that departed the UK and omitted arrivals and domestic legs. The airports that saw the most ghost planes were Heathrow, Aberdeen, Manchester, Stansted, and Norwich, according to the data.

The problem has continued into 2022, with some carriers voicing frustration over the rule, calling the flights "unnecessary." According to Lufthansa Group CEO Carsten Spohr, the German carrier saw a decline in winter bookings and canceled 33,000 of its scheduled flights as a result.

However, the reinstated slot policy requires the carrier to still fly 50% of those planes, regardless of if passengers are onboard.

"We have to make 18,000 additional, unnecessary flights in winter just to secure our take-off-and-landing rights," Spohr told a German newspaper in late December.

"While climate-friendly exemptions have been found in almost all other parts of the world during the pandemic, the EU does not allow this in the same way," he continued. "This damages the climate and is exactly the opposite of what the EU Commission wants to achieve with its "Fit for 55" program."

Introduced in July 2021, the "Fit for 55" program is the EU's plan to reduce carbon emissions by at least 55% by 2030. According to The Air Transport Action Group, the global aviation industry accounts for about 2% of the world's CO2 emissions.

However, climate activists say the EU's 50% requirement contradicts its 2030 goal. Environmentalist Greta Thunberg tweeted in January about Brussels Airlines flying 3,000 ghost planes.

Meanwhile, Aviation Environment Federation director Tim Johnson told The Guardian that the government "must act" to solve the problem of ghost flights.

"[The government's] recent claim earlier that aviation can be net-zero by 2050 while accommodating a 70% increase in passenger numbers (from 2018 levels) stretches belief when there are such obvious examples of inefficiency in the current system," Johnson said. "Fixing these should be a priority."

Nevertheless, the UK Department for Transport defended its decision in a statement to The Guardian, saying it "acted swiftly" during the pandemic to prevent ghost planes from flying, but some flights still may operate with low passenger volumes to carry "key workers or vital cargo."

While the reinstated slot rule is 50%, the UK government is scheduled to increase it to 70% this summer. Lufthansa spokesperson Boris Ogursky told CNBC in January that the decision is "appropriate," but carriers should be given more flexibility

"Due to the development of new virus variants and the resulting travel restrictions, the situation remains volatile, so exemptions are still necessary," he said.