THE HAGUE, Netherlands (AP) — Dutch passengers on KLM flights might have recognized the co-pilot's voice when he introduced himself on the airline's Cityhopper services.

It was not just their co-pilot telling them weather conditions and estimated time of arrival. It was their king.

King Willem-Alexander told national daily De Telegraaf in an interview published Wednesday that he has ended his role as a regular "guest pilot" on KLM's fleet of Fokker 70 planes after 21 years and will retrain to fly Boeing 737s.

The 50-year-old father of three and monarch to 17 million Dutch citizens calls flying a "hobby" that lets him leave his royal duties on the ground and fully concentrate on piloting the plane. He tells De Telegraaf, "that, for me, is the most relaxing part of flying."