Which country's King has regularly piloted commercial passenger jets?

It was reported in 2017 that King Willem-Alexander of the Netherlands had secretly been piloting commercial aircraft for Dutch airliner KLM for many years.

https://people.com/king-willem-alexander-netherlands-pilots-plane-united-states-queen-maxima-8661525

King Willem-Alexander of the Netherlands has secretly worked as a co-pilot for KLM Airlines for many years. He's qualified to fly commercial aircraft and used to fly twice a month, blending in with regular crews-most passengers never knew royalty was in the cockpit. He started with Fokker 70 jets and now flies a Boeing 737, including the Dutch government's official plane when needed. He says flying helps him unwind from royal duties and enjoy the focus of aviation.

https://time.com/4783688/dutch-king-willem-alexander-klm-pilot/