By OLIVER TREE
Last updated at 10:10 PM on 4th May 2011
They managed to penetrate Pakistani airspace, hover for 40 minutes, and flee undetected towards Afghanistan until the very last minute.
And now, pictures of the wrecked helicopter that crashed in Osama bin Laden's compound may shed new light on how Navy SEAL raiders snuck into Abbottabad without alerting Pakistani forces - by using secret 'stealth' helicopters.
Pictures of the downed chopper's heavily damaged tail section bear a striking resemblance to the smooth angular design of other stealth aircraft and have left aviation experts struggling to identify the unknown machine.
Scroll down for video
Stealth: The strange design of the rotor tail has led many to speculate that U.S. Navy SEALs used a secret stealth helicopter in Sunday's raids
Unknown: Distinctive features, such as the smooth and angular outer shell, covered rotor blades and pointed rear end have bamboozled aviation experts
The pictures have left aviation experts scratching their heads, with several concluding it must be a new, as yet unknown helicopter design.
Bill Sweetman, editor of Aviation Week said the pictures show a 'stealth-configuration' on the wrecked rotor housing.
He said: 'Well, now we know why all of us had trouble ID'ing the helicopter that crashed, or was brought down, in the Osama raid.
'It was a secretly developed stealth helicopter, probably a highly modified version of an H-60 Blackhawk.'
Citing pictures shown on MailOnline, he added: 'Photos show that the helicopter's tail features stealth-configured shapes on the boom and tip fairings, swept stabilizers and a 'dishpan' cover over a non-standard five-or-six-blade tail rotor.
'The willingness to compromise this technology shows the importance of the mission in the eyes of US commanders - and what we're seeing here also explains why Pakistani defences didn't see the first wave (at least) coming in.
'No wonder the team tried to destroy it.'
Standard: The UH-60 Black Hawk is a workhorse with U.S. forces, with over 1000 currently serving across the Army, Navy and Airforce
Comparison: The rotor of the crashed 'stealth' helicopter (left) from Sunday's raid and a close up of a standard UH-60 Black Hawk helicopter
It was previously thought that the Navy SEAL teams involved in last Sunday's attack used modified MH-60 Black Hawk or Sea Hawk variant helicopters in the raid - although the White House would not confirm or deny what type of helicopter was used.
Initially the plan was for the SEAL teams to 'fast rope' from the hovering 'Black Hawks', but according to the White House and defence officials, one of the helicopters developed a mechanical fault and had make a 'hard landing'.
Equipped: SEALs and other special forces have access to the latest military hardware, potentially explaining why they would have used an experimental or secret helicopter type
ID: The rear end bears no resemblance to that of the Black hawk typically used by special forces
As the U.S. special forces fled bin Laden's compound, they destroyed the crippled helicopter, leaving what they thought were only charred remains.
Discussing the intriguing pictures, a writer for website Defense Tech dismissed speculation the new craft was a modified version of the MH-60.
He said: 'All I’ll say is that it sure doesn’t look like it came off even a modified MH-60 Black Hawk. It looks like a stealthy new aircraft.'
Previous: Experts have speculated the 'clasified' helicopter could be a descendant of the now abandoned RAH-66 Comanche stealth helicopter project - seen here in prototype testing
Experts are now speculating the mysterious helicopter may be a descendant of the abandoned RAH-66 Comanche stealth helicopter project.
The Comanche, in development since 1984, reached the working prototype phase before it was cancelled in 2004.
It has been suggested that the military could have kept a few examples of the Comanche for use on high priority missions such as last Sunday's raid on the bin Laden compound.
The UH-60 Black Hawk helicopter, manufactured by Sikorsky, first entered service with the U.S. army in 1979.
Since then, the $44 million helicopter has become a workhorse across all branches of the American military, with U.S. forces currently operating 1,349.
There are numerous variations on the basic design, with special forces typically using the highly modified MH-60 variant.
The Black Hawk, which first began flying in 1978, has a crew of three or four and can carry 11 soldiers equipped for combat.
Eyes: 'The Beast of Kandahar' i.e. the secretive RQ-170 surveillance drone, was said to have filmed the daring raid and transmitted it back to the President in real time
The new 'stealth' helicopter may not have been the only secret weapon used last Sunday.
Navy SEAL teams have access to the latest weaponry and have the pick of any hardware deemed necessary to carry out the job.
It is alleged that during the killing of bin Laden in Abbottabad, the SEALS involved were supported by the Air Force's secretive RQ-170 pilot less drone- dubbed 'The Beast of Kandahar'.
The Air Force denied the futuristic looking weapons existence until 2009 and has never released an official photo of the reconnaissance aircraft.