Ernesto has left Florida's Atlantic coast and headed north and technicians have begun preparing for Wednesday's launch from the Kennedy Space Centre.
The launch window to send Atlantis into space to resume construction of the International Space Station was due to shut on September 7 but Nasa has an extra day to launch after its Russian partners delayed a re-supply mission to the space station.
Two spaceships could not be docked at the same time and, under the deal, the next launch of a Soyuz rocket to the space station will take place on September 18, not September 14.
Atlantis' mission will be the first by Nasa to resume construction of the space station since the Columbia disaster in 2003 when seven astronauts died when the shuttle fell apart over Texas.
Atlantis will be carrying a $372million truss segment that contains a second pair of power-producing solar arrays and a rotary joint to keep the panels tracking the sun.
The International Space Station
needs to be completed by 2010
Nasa needs to complete assembly of the half-built station before the shuttles are retired in 2010.
It was confirmed on Thursday that the Lockheed company has been awarded the contract to build the capsule-like spacecraft, Orion, that will replace the shuttles in 2010.
Nasa said the estimated value of the initial contract is $3.9billion over five years.
The first Orion launch with humans aboard is planned for no later than 2014, and for a return landing on the moon no later than 2020.
Orion will be capable of taking four crew members to the moon and, eventually, supporting transfers to Mars. It could also carry up to six crew members to and from the International Space Station.