The London Telegraph speculates:
An RAF C130 Hercules transport aircraft, believed to have been carrying SAS troops, crashed 20 miles north-west of Baghdad yesterday.
Rescue helicopters flew over the crash site searching for any sign of life. But with the wreckage said to be spread over a wide area there was little hope that anyone had survived.
At RAF Lyneham, Wilts, Wing Commander Nigel Arnold said: “We are in the process of contacting the families of those involved and until that is done I’m, afraid we will not be releasing any details of the crew.”
A senior US military officer in Iraq said the aircraft was on its way to the large US base at Balad, which is used by allied special forces to mount operations in a number of towns inside the so-called Sunni Triangle.
It was not immediately clear what caused the crash but the most likely explanation seemed to be that it had been shot down by insurgents. The incident is believed to mark the largest single loss of British personnel since the start of the war, almost two years ago.
A “special duties” aircraft would normally carry a crew of five or six. It could carry up to 128 passengers but in a special forces role, a maximum of 70 is more likely.
[…]
The worst loss of life for the SAS since the Second World War was in the Falklands when 18 members were killed. A total of 76 British servicemen and women have died since the start of the war in Iraq.If the aircraft was shot down, it would represent a major success for the insurgents who have been trying to disrupt the Iraqi elections. US aircraft and helicopters have been regularly targeted with shoulder-launched surface-to-air missiles. But although dozens of US helicopters have been brought down, until now no fixed-wing aircraft has crashed as a result of enemy attack.
[…]
RAF Hercules operating in Iraq are fitted with several types of so-called DAS counter-measures against the heat-seeking guidance sensors of the missiles.They are based at Basra International Airport or al-Udeid base in Qatar and make regular “milk run” flights to Baghdad airport with supplies for personnel at the British Embassy and nearby US military headquarters.
The only RAF C130s known to operate north of Baghdad are the “special duties” aircraft of 47 Sqn based at Lyneham.