An RAF whistleblower has told BBC Panorama about deep concerns among servicemen about the state of the UK's fleet of Nimrod spyplanes.
The insider, an airman with 20 years' experience, revealed a number of technical problems and fuel leaks, including an incident during a UK flight in November 2004 that he believed could have brought down the plane.
In the incident, he said, a hot-air pipe had ruptured below fuel tanks and superheated air had "blasted out", melting the seals.
Photographs of the damage showing scorching below the wing's fuel tanks and in the bomb bay were also passed to the programme.
The airman said: "Chances are, if they'd flown for a few hours more, we would have lost them. And the crew knew nothing at all about it. It was only when they landed that the damage was discovered."
But in an interview with the programme, Air Chief Marshal Sir Glenn Torpy, the Chief of Air Staff, denied there was a safety problem with the planes.
Panorama looks at the Kinloss-based fleet nine months after Nimrod XV230 crashed in Kandahar, Afghanistan, killing all 14 on board.
It was only when they landed that the damage was discovered
The plane had just completed air-to-air refuelling at 20,000ft when the pilot warned there was a fire on board.
Immediately after the incident, air chiefs dismissed Taleban claims that it had been shot down. They said the most likely explanation was a technical fault.
Since the crash there has been speculation that a fuel leak had caused the crash. An RAF Board of Inquiry into the crash has yet to report.
Panorama also uncovers details of two major fuel leaks, the first of which, according to former Nimrod engineer Jimmy Jones, could have caused the loss of another crew.
In November last year, just eight weeks after the Kandahar crash, a fuel pipe coupling was found to be leaking after air-to-air refuelling.
The crew thought it so serious that an air incident report was filed and mid-air refuelling procedures were changed.
Asked how serious he thought the incident was, Jones warned that it could have been a "replication" of the situation in September.
In December, sources told Panorama, a crew on another plane filed an incident report after leaks caused "pools of fuel" to form in the bomb bay and fuel covered flares.
Some of the families of three of the airmen who died have also revealed that their partners were concerned about some of the planes they were flying in.
Laura Robson, girlfriend of 26-year-old co-pilot Steve Swarbrick, said: "He was always complaining that the flights were always delayed because of maintenance issues. He was always saying that there was going to be an accident, a serious one."
The Nimrods entered service in 1969. Based in Morayshire, they were used as reconnaissance aircraft to hunt Soviet submarines. Now, with the War on Terror in Iraq and Afghanistan, they are using sophisticated technology to track insurgents in searing heat.
The US have replaced many of its ageing spyplanes with unmanned drones, like the Predator.
Retired Air Vice-Marshal Brian Robinson told the programme that operations in the Middle East were having a huge impact on the Nimrods.
He said: "They are doing a full pint job with a half pint of resources. That can't go on, it has to change."
Asked if he thought that air-to-air refuelling was safe, Sir Glenn Torpy told Panorama: "It's exactly the same as the rest of the integrity of the aircraft. It has been a focus for understandable reasons and we did suspend air-to-air refuelling for a period in November. We are looking at what we're doing. It is as safe as it needs to be."
He admitted to being "very concerned" about the number of fuel leaks. But he added: "That's why we've made sure we analysed every single incident. There are no underlying themes."
Panorama: On a Wing and a Prayer is on BBC1 on 4 June at 8.30pm
Ex-engineer Jimmy Jones said a fuel leak last year was serious
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Britain's Air Chief Marshal on the safety of Nimrods
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