Prince William, his wife Catherine and their three children took a budget airline flight on Thursday -- just days after his brother Prince Harry and wife Meghan faced criticism for their use of private jets.
The Duke and Duchess of Cambridge took their family on economy airline FlyBe for a flight from Norwich in eastern England to Aberdeen on Scotland's east coast. They were traveling to Queen Elizabeth's summer residence of Balmoral Castle, Reuters news agency reported.
"We were delighted to welcome the Duke and Duchess of Cambridge and their family on board one of our flights again, this time when they flew from Norwich to Aberdeen with our franchise partner, Eastern Airways," a FlyBe spokesman told CNN in a statement.
FlyBe declined to tell CNN how much the flight had cost. Prices for that route start at £73 ($89), with a fully flexible fare costing £249 ($303).
Kensington Palace told CNN that it had no comment on the matter.
Earlier this week, the Duke and Duchess of Sussex faced criticism after using private jets 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, given aviation is one of the world's major polluters and is responsible for more than 2% of global emissions.
The environmental footprint of a private jet is also much greater than that of a commercial plane.
Earlier in August, Harry said he plans to have two children "maximum," in order to protect the planet, during a conversation with activist Jane Goodall in an edition of British Vogue guest-edited by Meghan. He also spoke about the "terrifying" effects of climate change.
Singer Elton John defended the royal couple, however, and said media reports of their trips were "distorted and malicious." The star said he and his husband David Furnish had paid for the private jet to Nice for security reasons, and had made a donation to an environmental charity.
"After a hectic year continuing their hard work and dedication to charity, David and I wanted the young family to have a private holiday inside the safety and tranquility of our home. To maintain a high level of much-needed protection, we provided them with a private jet flight," he posted on Twitter.
A friend of Meghan defended her in a post on Instagram, calling out the "racist bullies" who criticize her, following years of "undeserved hate and abuse."