Airplane
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As coronavirus infections rise around the globe, demand for air travel is projected to hits its lowest point since the last financial crisis. Airlines around the world could lose up to $113 billion in revenue this year if COVID-19 continues to spread, the International Air Transport Association forecast on Thursday.

With travelers scarce, some carriers are turning to a troubling practice, the Times of London reports: flying planes with no passengers, in order to hang on to take-off and landing slots. On Thursday, the U.K.'s Secretary of State for Transport, Grant Shapps, posted a letter he sent to air travel regulators after learning of airlines operating "ghost flights" during the global outbreak. "Bad news for the environment, airlines & passengers," he tweeted.

The custom stems from the way airports manage their limited runway capacity. More than 200 of the world's busiest airports allocate specific time slots to airlines, which often pay top dollar for them. To manage demand, airlines are required to use their slots at least 80 percent of the time, or risk losing them to a competitor.

In order to maintain that 80/20 ratio, flying empty jets around is not an entirely uncommon industry practice, nor is it illegal. But given the growing scrutiny of air travel's climate toll, it is frowned upon, especially by U.K. regulators. Several British carriers that have since gone extinct, including British Mediterranean Airways, BMI, and Flybe (which declared bankruptcy this week amid plummeting demand for air travel), have all been reported to fly empty or mostly empty planes from London Heathrow in the past.

Shapps' letter to British air regulators asked them to suspend the 80/20 rule during the coronavirus crisis. The IATA has also requested that global air regulators suspend the rule until the fall, so that "airlines can respond to market conditions with appropriate capacity levels, avoiding any need to run empty services in order to maintain slots."

For reference, the average round-trip flight for a single passenger from Heathrow to Hong Kong produces about 1.82 metric tons of CO2, according to a flight emission calculator by The Guardian. That is more carbon pollution than the average person would emit in an entire year in 81 countries around the world.