NASA mission managers are seeking to delay the final two scheduled space shuttle flights, a move that — if approved — would push the last liftoff of the shuttle era to February 2011.

Under the proposed change, the final scheduled flight of Space Shuttle Discovery, the STS-133 mission currently slated for a Sept. 16 launch, would slip to Oct. 29. That delay would in turn push the last planned shuttle mission, the November flight of Endeavour on the STS-134 mission, to Feb. 28, 2011.

“The change request will be reviewed by all affected parties — the space station program, the astronaut office, mission controllers,” NASA spokesman Mike Curie said. “It’s being discussed but there has been no decision made yet.”

A final decision on whether to push back the flights will be made July 1, he said.

“They just need a little bit more time to get some of the spare hardware ready to fly on STS-133,” Curie said.

Discovery’s STS-133 mission will deliver spare parts and an Italian room called Leonardo to the international space station. Formerly a cargo pod, the Leonardo module has been refitted to serve as a permanent storage room on the space station. The mission will also carry a humanoid robot called Robonaut 2 for tests aboard the station.

NASA wants to haul as many large parts as possible on the final shuttle flights before the three-orbiter fleet is retired.

The payload on the final shuttle mission has also experienced some delays in processing. Endeavour is slated to carry the $1.5 billion Alpha Magnetic Spectrometer, an astrophysics experiment, to the station.

Scientists decided in April to replace a key magnet on the instrument with a more permanent one that would allow the experiment to run for a longer time on the orbiting laboratory.

The possible push to February for the mission, however, would simply be the result of the shakeup in the penultimate mission’s timeline, Curie said. If Discovery launches in October, November would likely be too quick a turnaround time to launch the last mission, he said.

Then, because of undesirable sun angles for the next few months, the next best time to launch would be in 2011. Several robotic cargo ships and a Soyuz vehicle with new station crew members are also due at the station in late 2010 and January 2011, complicating the shuttle launch opportunities, NASA officials have said.

“The next really available launch window is in late February,” Curie said.