Prince William surprised fellow travellers when he was spotted boarding a Ryanair flight to Glasgow last month. The future King was travelling to Scotland as part of his training to fly with the East Anglian Air Ambulance.
Wearing a navy blue jumper, pale shirt, trousers and glasses, a casually-dressed William could almost have been mistaken for any other passenger.
The Prince was believed to be accompanied by just one bodyguard.
Prince William was accompanied by one bodyguard on the flight
"The plane was delayed for about 20 minutes and nobody knew why," an eyewitness told The Sun. "Then when it landed we realised the Prince was on board."
"I never expected to see him on Ryanair, but it's refreshing to see a member of the royal family take a cheap flight," they added.
This is not the first time that William, 33, has chosen to board a no-frills airline. In 2011 the Duke and his wife the Duchess of Cambridge, née Kate Middleton, famously flew economy after the wedding of William's cousin Zara Phillips to Mike Tindall.
Kate and William also opted for a budget airline after Zara Phillips' wedding in 2011
The Duke and Duchess opted out of taking a private jet and instead flew with low-cost airline Flybe to make their trip from Edinburgh to Manchester. At the time William and Kate – whose parents Carole and Michael Middleton used to work for British Airways – travelled to the Northern city because they were based in Anglesey, where William was working with the RAF.
The couple, who had gone through the normal security procedures like everyone else, were then whisked off in a private car waiting for them at the airfield.
Prince Harry, meanwhile, headed back to London after the wedding via Easyjet.
The couple's daughter Princess Charlotte will be christened later this week
Later this week William and Kate will celebrate the christening of their newborn daughter Princess Charlotte. The royal baby, who was born on Saturday 2 May, will be baptised in the same church as William's late mother Princess Diana – St Mary Magdalene Church on the Queen's Sandringham Estate.
The ceremony will most likely be attended by the Queen and Prince Phillip, William's father Prince Charles and his wife the Duchess of Cornwall, and Kate's parents Carole and Michael.
Princess Charlotte's godparents are likely to be announced on the day of the event.