Days after Prince Harry and the Duchess of Sussex Meghan faced criticism from activists about their use of private jets, Prince William, Kate Middleton, and their three children took a budget airline flight on Thursday.

The family was traveling to Queen Elizabeth's summer residence of Balmoral Castle in Royal Deeside, on economy airline FlyBe for a flight from Norwich to Aberdeen, Reuters reported.

"We were delighted to welcome the Duke and Duchess of Cambridge and their family onboard one of our flights again, this time when they flew from Norwich to Aberdeen with our franchise partner, Eastern Airways," CNN quoted a spokesperson for FlyBe as saying. 

However, FlyBe declined to comment on the cost of the flight. Prices for the Norwich-Aberdeen route start at £73 ($89), with a fully flexible fare costing £249 ($303).

The criticism of Harry and Meghan's use of private jets stems from a conversation Harry had with activist Jane Goodall, in an edition of British Vogue guest-edited by Meghan. In it, Harry stated that he would only have a maximum of two children, citing the need to protect the planet. He also spoke about the "terrifying" effects of climate change.

However, earlier this week, Harry and Meghan used 4 private jets in 11 days to fly to the south of France and Ibiza in two trips just days apart.

Environmental campaigners accused the pair of hypocrisy, saying that Harry and Meghan's actions contradict their public stance on climate change.

Kensington Palace said that it did not have any comment on the matter.

Aviation is one of the world's major polluters and is responsible for more than 2% of global emissions, with the environmental footprint of a private jet being much greater than that of a commercial plane.

Prince William, Kate Middleton Prince William, Middleton meets with Irish Guards after attending the St Patrick's Day parade at Cavalry Barracks in Hounslow, where they presented shamrock to officers and guardsmen of 1st Battalion the Irish Guards on March 17, 2019 in Hounslow, England. Photo: Getty Images/Gareth Fuller-WPA Pool