The two crewmen of an RAF Tornado jet who were killed in Iraq have been named.
It is thought a Patriot missile hit the plane
They were Flight Lieutenant David Rhys Williams and Flight Lieutenant Kevin Barry Main, who served with 9 Squadron, RAF Marham.
The pair were pilot and navigator of a GR4 Tornado which was shot down by an American Patriot missile near the Kuwaiti border on Sunday.
A major investigation by British and American forces is under way.
The friendly fire - or "blue on blue" - incident happened as the aircraft returned from a mission over Iraq on Sunday morning.
On Monday Wing Commander Mike Oldham, acting Station Commander at RAF Marham in Norfolk, confirmed the deaths.
He said: "They were returning from one of many successful and professionally conducted missions in Iraq, and I would like to pay tribute to their expertise and dedication."
Wing Commander Oldham added: "Our thoughts and prayers are, of course, with the families and friends of the air crew concerned.
"Here at RAF Marham we live and work as a very close team - today we have lost two valued members of that team."
Group Captain Al Lockwood, chief spokesman for the British forces, said: "This is a tragedy and we are taking rapid steps to find out the reason and to ensure that there is no repetition."
The Patriot system is in the Gulf to protect Kuwait and coalition forces from incoming missiles.
UK Defence Secretary Geoff Hoon, who sent his sympathies to the families of the crew, said there were a set of procedures in place to defend British and coalition forces.
"Sadly on this occasion they have not worked and we are conducting urgent reviews, both of the operation of missile batteries as well as of our own aircraft to ensure that this cannot happen again," he told the BBC.
Air Marshal Brian Burridge, commander of British troops in the Gulf, said the accident would not deflect troops from their mission.
He told the BBC: "This is a sad moment but we will put it behind us as quickly as we can in a military sense and carry on to our objective."
RAF Group Captain Jon Fynes said the accident would not harm the coalition, arguing "in many ways it brings us closer together".
"At the base they are sad it happened, but they are now refocused on what needs to be done next."
William Farish, the US ambassador to Britain, paid tribute to the Tornado crew.
He told the BBC: "Friendly fire is something we have lived with for ages throughout wars, but to have it happen in a way like this is very sad."