He will join the East Anglian Air Ambulance, his office has confirmed to PEOPLE.
Since leaving the RAF at Anglesey, where he was based for more than three years, William, 32, has been eager to get back to flying and is set to complete what officials call "a mandatory period of training this autumn and winter."
He will start work at the area bases at Cambridge and Norwich airports in spring 2015, flying night and day shifts, which will allow for him and wife Kate, also 32, to live primarily at Anmer Hall, their 10-bedroom mansion near Sandringham.
The home is undergoing renovations and it is known that the couple want to use it as their base. Although Kensington Palace is the main official residence, they will settle in their country home. "They want to live up there as much as possible," a source close to them tells PEOPLE.
"They are going to be Norfolk-based and coming to London every so often, rather than London-based and going off for a weekend in Norfolk," the source says.
William's spokesman says the prince will start as a co-pilot, but after a period of training, will be qualified to fly as a helicopter commander.
The job is to be his primary occupation, "but his roster will take into account the duties and responsibilities he will continue to undertake on behalf of The Queen, both in the United Kingdom and overseas," his spokesman says in a statement.
William plans to continue his work with his patronages and with the Royal Foundation of The Duke and Duchess of Cambridge.
In common with all other East Anglian Air Ambulance pilots, William will be formally employed by Bond Air Services. He will draw a salary, which he will donate in full to charity.
He will begin training for his air transport pilot's license in September, which is estimated to take a minimum of five months, culminating in 14 examinations and a flight test.