The event focused on paying respect to the service members as the operation is coming to an end after 75 years. It was a homecoming for William and Kate, who were based in Royal Air Force Valley from 2010-13 as the Duke worked as helicopter co-pilot for the Search and Rescue Training Unit.
"During this time, His Royal Highness undertook a total of 156 search and rescue operations, resulting in 149 people being rescued," the royal palace wrote on Instagram.
On the reflective day, William's former squadron commander, Sparky Dunlop, told reporters the royal was a "very good pilot," adding: "He would live and work with his crew, go on rescues with his crew, eat with his crew. He was just another one of the guys."