CAPE CANAVERAL, Fla. -- U.S. flags flown in space to honor those lost in the Sept. 11, 2001 terrorist attacks were presented to their families during a Flag Day ceremony in New York City.

The event included a message from the Expedition Four crew, who spent the day packing up for a planned return to Earth on Monday.

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Some 6,000 small American flags, one large flag that was recovered from the World Trade Center debris and other momentos representing fire, police and other emergency officials that flew in space last December were given to city and state officials.

NASA Administrator Sean O'Keefe -- along with astronauts Frank Culbertson, Linda Godwin, Dom Gorie and Mike Massimino -- represented the space agency.

"The tradition of carrying American flags into space dates back to the very beginning of this historic agency," O'Keefe said.

"From the surface of the Moon to the unchartered regions of our galaxy, NASA has flown the American flag as a patriotic symbol of truth, honor and justice. It is appropriate that we present this flag back to the city of New York on Flag Day," he said.

Culbertson, who was Expedition Three commander and the only American in space on the day of the attacks, recalled his observations of New York that day.

Following the initial delivery of the bad news, Culbertson remembered how difficult it was to learn what was happening from Mission Control in Houston after that facility was shut down and flight controllers were moved to a back up site as a security precaution.

Eventually he received news in English from Russian flight controllers in Moscow, telling the audience that it was a great example of international partners working together in space.

The moving ceremony stole the show from events 245 miles in space as the crew of shuttle Endeavour began winding down its mission to the International Space Station (ISS).

The major task for Friday was to close up the Italian-built Leonardo supply module, remove it from the side of the Unity node on the ISS and latch it back in place in the shuttle's cargo bay.

French astronaut Philippe Perrin was the key operator of Endeavour's robot arm and successfully stowed the "moving van" without any trouble at 4:12 p.m. EDT (2012 GMT).

Earlier in the day the shuttle's steering jets were used a third and final time to boost the station's orbit by a total of some four miles (6.4 kilometers).

Endeavour remains scheduled to undock with laboratory complex at 10:32 a.m. EDT (1432 GMT) Saturday and land back at the Kennedy Space Center at 1 p.m. EDT (1700 GMT) Monday.

The early weather outlook for an on time landing in Florida is good.

Meanwhile, Canadian engineers continue to troubleshoot a problem detected late Thursday with the new robot arm work platform that was installed this week with the help of spacewalking astronauts.

The problem is that the platform, also known as the Mobile Base System, won't power up the Canadarm2 as planned. The system must work to support the future growth of the space station.

However, mission managers are almost positive the trouble is with the software used to control the power up process and that a relatively simple change in coding should take care of the situation.

"It's looking more and more like a speed bump," said shuttle flight director Paul Hill.