This story was updated at 10:22 p.m. EDT.

HOUSTON - Astronauts aboard NASA’s shuttle Endeavour converted their spacecraft into a 100-ton glider Tuesday as they head home from a packed construction flight to the International Space Station (ISS).

Endeavour commander Dominic Gorie and pilot Gregory H. Johnson fired thrusters and tested flight control systems that will allow their spacecraft to once more fly through the Earth’s atmosphere for a planned Wednesday landing in Florida.

“In my view, it’s been an extraordinary way in every way that I can think of,” said LeRoy Cain, chair of Endeavour’s STS-123 mission management team, on Monday. “It’s just been a textbook mission up and down the line.”

Endeavour and its crew departed the space station late Monday after 12 days of joint orbital construction - the longest period yet for a visiting crew. They performed a record five spacewalks while at the station to install an attic-like storage module for Japan’s massive Kibo laboratory and construct a Canadian-built maintenance robot affectionately dubbed “Mr. Dextre.”

“We’ve done just awesome,” Gorie said of his crew before leaving the station.

The astronauts also left Endeavour’s heat shield inspection boom attached to the ISS so the crew of NASA’s next shuttle to fly can haul the rest of Japan’s school bus-sized Kibo lab to the station. That module, set to launch May 25 aboard Discovery, is so large the shuttle cannot carry its own inspection pole.

During a break in their flight systems checks, Johnson and crewmates snacked on what appeared to be jelly beans, which they playfully tossed around – bag included - while floating in Endeavour’s flight deck.

“We appreciate the entertainment, unfortunately we have to ask you to get back to work here a little bit,” Mission Control radioed up to the crew. The rest of the checkouts went well.

Returning to Earth

Gorie and Johnson also fired Endeavour’s thrusters today in an ultra-brief maneuver, just six seconds at most, to gain an extra 4 feet per second (1.2 mps) in velocity.  But the small boost gives their spacecraft two chances to land at NASA’s Kennedy Space Center in Cape Canaveral, Fla., on Wednesday.

The first landing opportunity arises before sunset at 7:05 p.m. EDT (2305 GMT), with a second window opening at 8:39 p.m. EDT (0039 March 27 GMT). Early forecasts from NASA’s Spaceflight Meteorology Group here at the Johnson Space Center predict favorable conditions at landing time.

“We’ve had a really great time up here,” said astronaut Mike Foreman, a mission specialist who performed three of the five spacewalks during Endeavour’s flight. “But yeah, I think a few of us are thinking about getting back to planet Earth.”

One such spaceflyer is French astronaut Leopold Eyharts, who arrived at the station during a February shuttle mission to install and outfit the European Space Agency’s (ESA) Columbus laboratory. NASA astronaut Garrett Reisman, who launched with Endeavour’s crew, replaced Eyharts as a member of the station’s Expedition 16 crew.

“Up to you Garrett, it’s your turn,” Eyharts said as he passed his flight engineer mantle to Reisman. “C’est la vie.”

Astronauts will due to spend some time today setting up a special recumbent seat on Endeavour’s middeck that will allow Eyharts, who will have spent almost 50 days in space by landing, to weather the return to Earth’s gravity in a reclined position.

“I’m preparing for that,” Eyharts said. “I’m trying to do exercises regularly, but I’m quite confident because just a couple of months is not so much.”

Mission Control woke Endeavour’s crew this morning with the Italian song “Con Te Partiro” by Andrea Bocelli in an orbital tribute to Eyharts’ homecoming.

"I'd like to see everybody back on Earth," Eyharts told flight controllers. "Thanks a lot for the music and see you very soon."

Station traffic heats up

Eyharts said he was more worried about his former station crewmates - Expedition 16 commander Peggy Whitson and flight engineer Yuri Malenchenko - who are on a six-month mission and have a busy few weeks ahead of them with Reisman.

The ESA’s first unmanned cargo ship Jules Verne is due to make the first of two test approaches at the station on Saturday before docking in earnest on April 3. A relief crew for also due to launch on April 8 aboard a Russian rocket, kicking off a busy handover that will end with the April 19 landing of Whitson, Malenchenko and a South Korean astronaut to arrive with their replacements.

NASA, meanwhile, is also forging ahead with plans for Discovery’s STS-124 mission to deliver the main section of Japan’s Kibo lab to the ISS. The shuttle’s external fuel tank is due to arrive at the Kennedy Space Center as early as today, mission managers have said.

Cain said the U.S. agency is also looking at ways to streamline streamlining the manufacturing and testing of new, modified shuttle fuel tanks to avoid delays that may impact flights later this year, such as the planned Aug. 28 launch of Atlantis to overhaul the Hubble Space Telescope.

“We’ll take the time we need to work through the problem and it’s not going to be an impact from a station assembly standpoint,” Cain said.

This story was written at NASA’s Johnson Space Center in Houston and updated in Cape Canaveral, Fla. SPACE.com staff writer Clara Moskowitz contributed to this report from New York City.

NASA is broadcasting Endeavour's STS-123 mission live on NASA TV. Click here for SPACE.com's shuttle mission coverage and NASA TV feed.

• NEW VIDEO: Space Station's Dextre Robot, AKA 'Gigantor'
• NEW GALLERY: Launch Day for Shuttle Endeavour
• NEW VIDEO: Japan's First Space Station Module