One RAF engineer died when a Red Arrows Hawk jet crashed following an incident in north Wales, a spokesman has said.
It is understood the Red Arrows aircrew had been at RAF Valley for routine Hawk simulator training - something that takes place once a month.
They had just taken off from the base and were on their way back to RAF Scampton, where the aerobatic team are based, when the incident happened.
The Hawk fast jet has been left destroyed by the crash.
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."
Caterer Anne Wilson, who works at The Anglesey Golf Club, situated at the end of the runway at RAF Valley, witnessed the aftermath of the crash.
The 52-year-old told the Press Association: "I did not see the crash but I heard a very loud noise.
"We are used to the planes going over but this was unusual, it was different to what we normally hear around here.
"I did go and have a look and there was a big fireball and lots of dark smoke ... quite a few of the members actually saw it.
"They said the plane came in quite steeply and saw a pilot eject, but that it was very low to the ground when they ejected."
She said the air ambulance was at the scene "for a very long time".
A spokeswoman for the Welsh Ambulance Services NHS Trust said: "We were called shortly before 1.30pm this afternoon to reports an aircraft had crashed at RAF Valley in Holyhead.
"We sent an emergency ambulance and a Wales Air Ambulance to the scene."