A redesigned space shuttle fuel tank has arrived at Nasa's Kennedy Space Center ahead of the vehicle's first flight since the Columbia disaster.
All the major shuttle components are now at Cape Canaveral
The delivery means all major shuttle flight components - orbiter, solid rocket boosters and the tank - are at the spaceport and ready for assembly.
The 47m-long, bullet-shaped vessel was removed from a barge and rolled into the assembly building on Thursday.
Nasa officials say the shuttle is still on for its scheduled May 2005 launch.
"It is the safest tank we've ever made," said Nasa's external tank programme manager Sandy Coleman.
Managers said the delivery was a first tangible sign of the two-year effort to return the shuttles to flight following is nearing its end.
The US space agency's remaining three vehicles have been grounded since Columbia broke up during re-entry on 1 February 2003, killing seven astronauts.
Investigators found the accident was caused by damage to the shuttle's wing.
During launch, a chunk of foam insulation broke off from Columbia's external tank and gouged a hole in the orbiter's left wing.
Super-heated air got inside during re-entry and caused the shuttle to disintegrate.
The insulating foam was found to have broken off from the bipod fitting, which connects the shuttle to its tank.
On the new version, this fitting will use four rod-shaped heaters instead of insulating foam to prevent ice build-up.
This should minimise the foam shedding that proved so disastrous to Columbia, officials say.