Olympic parachutist Mark Sutton's reportedly fatal accident is understood to have happened on the first day of a three-day wingsuit event near Martigny, in the Valais canton, near the French border.
Mr Sutton had been very experienced in using the special jump suits, which increase the surface area of the body and act like a parachute wing, allowing users to glide through the air at high speeds.
A video on Mr Sutton's YouTube account shows him in several wingsuit flights, including this one near Riva del Garda in northern Italy in August last year, which he introduces with a reference to Team GB:
More top news
Mild, muggy air to end the weekend
James Ketchell has completed his epic 175-day journey in a James Bond-style gyrocopter.
The hair stylist, who rose to fame on the Netflix hit show Queer Eye, has said he has been living with HIV.