Update 6.35pm: One RAF engineer died when a Red Arrows Hawk jet crashed following an incident at RAF Valley in north Wales, a spokesman has said.
Group captain Nick Tucker-Lowe said in a statement: "It's with great sadness that the RAF can confirm the death of an engineer from the RAF aerobatics team The Red Arrows in a tragic accident today.
"The engineer's family have been informed and have asked for a 24-hour period of grace before further details are released.
"The pilot of the aircraft survived the incident and is currently receiving medical care."
Defence secretary Gavin Williamson said: "Our thoughts and prayers are with the family, friends and colleagues of the RAF engineer at this incredibly sad time."
Earlier: Red arrows jet crashes after incident at RAF Valley
A Red Arrows jet has crashed after an incident at RAF Valley in north Wales, the Ministry of Defence has said.
It is understood there were two people on board the Red Arrows jet aircraft which crashed on Tuesday.
"We are aware of an incident today at RAF Valley involving a Hawk aircraft," a Ministry of Defence spokesman said.
"We are investigating the incident and it would be inappropriate to comment further at this stage."
North Wales Police confirmed they were in attendance and were called to the scene at around 1.50pm.
The world-famous aerobatic team performs stunts and daredevil displays, and flies the distinctive Hawk fast-jets.
Based at RAF Scampton in Lincolnshire, all Red Arrows pilots have flown operationally in frontline aircraft before joining the display team.
Some 1,500 service personnel, civil servants and contractors work at RAF Valley on Anglesey, which is also home to the military's search-and-rescue, post-crash team.
August 2015 - Eleven men were killed when a vintage Hawker Hunter jet plummeted on to the A27 in West Sussex during a loop-the-loop stunt at the Shoreham Airshow. A further 13 people, including the pilot Andy Hill, were injured.
The disaster led to the cancellation of the Red Arrows performing stunts at the Farnborough Air Show for the first time in more than 50 years over safety fears.
August 2015 - RAF-trained fast jet pilot Kevin Whyman, 35, was killed when his Folland Gnat aircraft plummeted during an aerial display at the CarFest event in Oulton Park, Cheshire.
November 2011 - Highly experienced Red Arrows pilot Sean Cunningham, 35, was fatally injured when he was ejected from the cockpit of a Hawk T1 aircraft while on the ground at RAF Scampton, Lincolnshire. A coroner ruled that the safety pin on the ejector seat had been "entirely useless".
August 2011 - Red Arrows Flight Lieutenant Jon Egging, 33, was flying a Hawk T1 when it came down into a field after he pulled six times the force of gravity at an air show near Bournemouth Airport, killing him instantly.
September 2007 - James Bond stuntman Brian Brown, 49, died when he crashed a Second World War Hurricane after carrying out an unplanned barrel roll at a re-enactment of the Battle of Britain at Shoreham Air Show, West Sussex.