The Hawk aircraft crashed at the air base on Anglesey Island in north Wales.
The pilot’s condition is not yet known.
The Welsh Ambulance Service said it was called shortly before 1.30pm on Tuesday to reports an aircraft had crashed at RAF Valley in Holyhead.
A spokesman said they sent an emergency ambulance to the scene and Wales Air Ambulance is also in attendance.
Sky News Defence Correspondent Alistair Bunkall said it is believed the aircraft was a two person plane.
The RAF is asking anybody with photographs of the incident to send them in to help with an investigation.
Prince William served with the RAF’s Search and Rescue Force at the Anglesey air base for three years.
RAF Valley is used as a training base for the Hawk aircraft which is part of the the Red Arrows team.
Famous for their red, white and blue vapour trail, impressive stunts and trademark diamond formation they are a familiar sight at air shows and military parades.
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