The heir apparent to the throne, Prince William is set to become an air ambulance pilot rather than take on full-time royal commitments.
After stepping down as an RAF search-and-rescue pilot over a year ago, the prince is said to have a "day job" with the East Anglian air ambulance service near his country home at Anmer Hall in Sandringham.
The role would involve 10-hour shifts working on a five-day rota, with three days off.
The majority of air ambulance pilots have a military background and have landed helicopters in some of the most inhospitable regions of the world, including combat zones.
The East Anglian Air Ambulance began thanks to an appeal launched in 2000 by jockey Frankie Dettori. He was a passenger on the plane that had crashed, killing the pilot. Because the region had no air ambulance service at the time, another aircraft flew the casualties to Addenbrooke's Hospital in Cambridge.
According to a Sunday Times report, Prince William told aides that he is not ready for full-time royal engagements. He is supported by father, Prince Charles, who has expressed regret about leaving his Royal Navy post too soon.
"The duke is fully committed to his foundation and charities, but he feels he had not yet got flying out if his system," said a royal aide.
"Should the duke and duchess grow their family, the duke is keen to take on a role which enables him to see them most days. The royal family is fully supportive of the plan."
On 29 May, the Duke and Duchess of Cambridge will visit an air ambulance team during a trip to Crieff, near Perth.
Kate Middleton wrote a foreword to a book about RAF wives which will be published next week: "I cannot pretend that I didn't feel anxious at times when William was on shift in howling gales, knowing that he was out flying in extremely challenging conditions, but he loved doing it and I always felt incredibly proud of him."
Prince William is taking what palace aides have called a "transitional year". He is spending time raising his son George as well as working for the United for Wildlife charity, which campaigns against illegal hunting.