London - Britain's Mail on Sunday says it has uncovered a major royal security breach by using an inexpensive app to track Prince William's air rescue ambulance while it is in the air.
The paper said the £2.99 ($4.65) app allowed it to keep close track of William as he flew in his capacity as a private pilot with East Anglian Air Ambulance in eastern England.
It said the app allowed its journalists to pinpoint where William was planning to land the air ambulance helicopter.
It published photos claiming to show William's helicopter landing and of the prince himself talking to colleagues on the ground.
The paper said that William's helicopter flies at low altitude at a relatively slow speed. For a small extra fee, the Mail on Sunday said, users can receive a text alert every time the helicopter William uses takes off on a mission.
William's press office refused to comment on the report, calling it a security matter. The Metropolitan Police also refused to comment.
The prince returned to work several weeks ago after paternity leave following the birth of Princess Charlotte.
He and his fellow crew members fly a H145 helicopter equipped with medical gear. He previously made similar rescues while serving at a Royal Air Force on an island off the coast of Wales.
He often rescued hikers who were lost or stranded and also aided road crash victims.
Those were military flights not believed to be easily tracked by commonly available apps.