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
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.'