Prince William, second in line to the British throne, paid a secret visit to Afghanistan to meet frontline British troops, his office said on Wednesday.
A spokesman said the 25-year-old prince, recently awarded his Royal Air Force (RAF) wings after a training course, flew a military transport plane for part of the journey to Kandahar.
He spent three hours with British service personnel at the airfield before returning home, the spokesman said.
The trip made headlines in British newspapers on Wednesday but sparked questions about whether it was simply a public relations exercise.
William was criticized recently for flying military Chinook helicopters to a bachelor party for his cousin and to his girlfriend Kate Middleton's family home.
"The cynics amongst us will say it's an attempt to cover up the Chinook jollies," former royal protection officer Ken Wharfe told BBC television.
Permission for the trip on Monday was given by William's grandmother, Queen Elizabeth, and his father, Prince Charles.
"The purpose of the trip was for the prince to familiarize himself with the operations of the RAF in theatre," a spokesman said, adding that the 30-hour trip had "passed without a hitch".
The prince flew in a C-17 Globemaster military transport plane which left a Royal Air Force base on Sunday, arriving in Afghanistan the next day. He flew back home via Qatar.
William's younger brother Harry served for 10 weeks with British troops in Helmand province earlier this year.
His tour of duty was abruptly cut short when a media blackout was broken and military chiefs began to fear for his safety as a prime target for a Taliban attack.
William's trip came after four months of training with the Royal Air Force that ended at a graduation ceremony where he was presented with his wings by his father.