Washington: The elite US Navy SEALs team used top secret, never-seen-before stealth helicopters to swoop down on an unsuspecting Al Qaeda chief Osama bin Laden in his Abbottabad safe haven and shoot him dead.
One of the secret choppers was disabled during the raid by the SEALs, blowing it up in an apparent bid to ensure that the frontline technology did not fall into non-US hands, US media reports said.
The secret choppers have been kept under wraps by Pentagon and their use for the key mission suggests that the American military planners did not want to take any chances in the high-risk raid.
Pentagon officials are still keeping mum on whether or not stealth choppers were used, but ABC news citing American aviators said that photos of what survived the explosion has sent military analysts buzzing about a stealth helicopter programme that was only rumoured to exist.
Former defence officials say the modified variant of the Sikrosky H-60 Blackhawk features extra blades on the tail rotor allowing it to fly significantly less noisily and also has low-observable technology similar to that of F-117 stealth fighter to enable it to evade Pakistan Air Force detection radars.
The US did not warn Pakistan about the raid for fear of leaks, but the helicopters nonetheless managed to fly to the compound from their base in Afghanistan without the Pakistan military seemingly being alerted.
The choppers appear to have a modified tail boom to a noise-reducing covering on the rear rotors and a special high-tech material similar to that used in stealth fighters.
Top former Pentagon officials say the bird is like nothing they have seen before.
"This is a first," they said. "You wouldn't know that it was coming right at you. And that's what's important, because these are coming in fast and low, and if they aren't sounding like they're coming right at you, you might not even react until it's too late...That was clearly part of the success."
In addition to the noise-reducing modifications, a former special operations aviator told The Army Times the general shape of what was left of the craft - the harsh angles and flat surfaces more common to stealth jets - was further evidence it was a modified variant of the Blackhawk.
Neighbours of bin Laden in Abbottabad, Pakistan, told ABC News they didn't hear the helicopters the night of the Sunday raid until they were directly overhead. The rotor covering, along with a special rotor design, suppressed the choppers noise.
The US has attempted to use stealth helicopters before. In the mid-90s, the Army developed several prototypes of the Comanche helicopter, a reconnaissance helicopter that was, at the time, a revolutionary step in stealth technology.
But in 2004 the Department of Defense scrapped the programme and promised to use technology developed for the Comanche on other crafts.
Since, the government has been working to silence the Army's Blackhawk helicopters but an official programme for the stealth choppers was never publicised. The wreckage, officials said, is the first the public has ever seen of an operational stealth-modified helicopter.
They believe that the stealthy Blackhawks have been in use for years without the public's knowledge.
"We probably have been running hundreds of missions with these helicopters over the last half dozen years, and the fact is, they've all been successful - or at least the helicopters have all come back," they said.
But now that one went down and photographs emerged of large sections being taken from the crash site under a tarp, former White House counter-terrorism advisor Richard Clarke said US officials may have reason to worry about where those parts end up.
"There are probably people in the Pentagon tonight who are very concerned that pieces of the helicopter may be, even now, on their way to China, because we know that China is trying to make stealth aircraft," he said.
The Chinese military is known to have a close relationship with the Pakistani military.