Delta Air Lines has admitted running empty planes from the US to Heathrow as part of Australian quarantine regulations, angering environmentalists.

Delta is not allowed to carry out the quarantine treatment in the US so has to fly the empty Boeing 777s to the nearest airport with facilities sanctioned by the Australian authorities which is Heathrow.

Authorities in Australia require inbound flights to be sprayed with insecticide to prevent against malaria and dengue fever.

A Delta spokeswoman said: “The Australian Quarantine & Inspection Service requires all aircraft operating to and from Australia are treated with insecticide by certified technicians at airports around the world.

“Materials used for this process are approved and available for use in the United States. However, according to US regulations, these treatments must be carried out at designated AQIS locations outside the United States.”

The airline confirmed it is planning to stop its disinfection trips to Heathrow at the end of the month, but is expected to switch to a Chinese airport.

Speaking to the Guardian, Richard George, of environmental group The Campaign for Better Transport, said:

“It symbolises their cavalier approach to the environment,” said Richard George, a campaigner at CBT.

The Delta “ghost flights” come after BMI, Heathrow’s second largest carrier, admitted flying empty planes from Heathrow to Cardiff to retain its lucrative takeoff and landing slots.