High explosives? This door is beginning to take on mythological properties.
Seriously, any shipyard or commercial construction site has hand operated tools that would make short work of the door - but you would have a hard time getting them past security. After all, somebody had to fabricate the thing.
the door exists to prevent the plane from being turned into a weapon, but it assumes that all pilots have good intentions. It was probably the wrong response to 9-11, since nobody will ever again sit meekly while terrorists try to take over a plane.