But the pilots need some rainy weather around Cape Canaveral to clear out over the course of the morning. Otherwise, they'll be forced to detour to the west coast of Florida and make a pitstop at MacDill Air Force Base in Tampa. It will be a real-time call as the ferryflight progresses.

A weather reconnaissance plane and the 747/shuttle duo are departing Barksdale this hour to head for Florida. The flight time will be about two-and-a-half hours.

But there's showers around KSC this morning. If the conditions don't clear over the next couple of hours, the ferryflight team would go to Tampa and wait for better weather at the spaceport.

"The team will have to make real-time decisions and see whether those storms break up and Discovery can touch down at the Shuttle Landing Facility once the 747 and pathfinder aircraft near Florida's east coast," an agency spokesperson says. "If not, the ferryflight team plans to divert to MacDill Air Force Base in Tampa, Florida to refuel and temporarily wait for a break in the weather."

Takeoff from Louisiana has been targeted for 10 a.m. EDT (9 a.m. local), if the weather permits. That would result in the shuttle arriving at Kennedy Space Center before 1 p.m. EDT.

The 747 and space shuttle Discovery will remain at the military facility in northwestern Louisiana for the evening. NASA does not conduct segments of the cross-country trip at night. The voyage will continue tomorrow morning, weather permitting.

By getting to Barksdale today, the ferryflight can make a straight trek to Kennedy Space Center in Florida without having to stop for fuel along the way. The preliminary plan has Discovery arriving home around 10:30 a.m. EDT.

This 50-minute stint by the Shuttle Carrier Aircraft will fly to northwestern Louisiana to spend the night at Barksdale Air Force Base.

Strict weather rules about clouds, cold temperatures and avoiding flight through rain govern where the Shuttle Carrier Aircraft can go. In addition, NASA ensures that Discovery won't be subjected to any bad weather while on the ground during a stopover. The guidelines are meant to protect the spacecraft and its delicate heat shield tiles.

The unique duo could resume the ferryflight this afternoon, weather permitting, and head for the planned overnight stay at Barksdale Air Force Base near Shreveport, Louisiana. But if the upcoming weather briefing shows Mother Nature won't cooperate, Discovery could spend the night in Fort Worth.

Arrival back at the shuttle homeport at Kennedy Space Center in Florida is targeted for Monday.

The aircraft have a wingspan of 195 feet, a length of 231 feet, a height to the top of the cockpit area of 32 feet and a maximum gross taxi weight of 713,000 pounds. They are powered by four Pratt & Whitney JT9D-7J gas turbine engines, each producing 50,000 pounds of thrust. Minimum crew for a flight is two pilots and one flight engineer. Minimum for a flight with the shuttle aboard is two pilots and two flight engineers.

The 747 will be refueled while managers assess the weather for taking the next step in the ferryflight. Today's goal is getting to Barksdale Air Force Base near Shreveport, Louisiana.

After getting airborne toward the southwest from Runway 22, the carrier aircraft banked to the left for a U-turn to head eastward over Bartstow and then onward as it climbed to the cruising altitude of 15,000 feet.

The 747 and Discovery are bound for the a refueling stop at Rick Husband International Airport in Amarillo, Texas. The ferryflight should resume later in the day, weather permitting, and continue pushing toward the east, eventually reaching a planned overnight stay at Barksdale Air Force Base near Shreveport, Louisiana.

The shuttle spent eight-and-a-half days in the Mojave Desert following its landing there to conclude its equipment-delivery mission to the International Space Station. Bad weather in Florida prevented Discovery from landing at Kennedy Space Center and forced Mission Control to divert the shuttle to the backup site at Edwards Air Force Base.

Technicians spent several days safing onboard systems and readying the shuttle for its ferryflight trip. After an aerodynamic tailcone was installed, the 110-ton spaceplane was lifted on top of the aircraft and secured in place.

Once back home, Discovery will be prepared for a scheduled March launch on another flight to the space station.

Attachment of the shuttle aboard the 747 has been completed at the gantry-like Mate/De-Mate Device structure. The orbiter was been hoisted up and the aircraft towed underneath Discovery for the duo to be bolted together. The work was finished overnight.

The flight plans call for departure at 6:20 a.m. local time (9:20 a.m. EDT) to head eastward on the initial segment of the coast-to-coast trip. The first refueling stop is planned at the Rick Husband International Airport in Amarillo, Texas.

Another intermediate stop for fuel is expected later in the day. NASA hopes to get Discovery to Louisiana on Sunday for an overnight stop at Barksdale Air Force Base near Shreveport.

"The low pressure weather system that forecasters have been monitoring for the last several days is expected to begin moving to the northeast and that would allow the ferryflight to reach Barksdale tomorrow," a NASA spokesman says.

Arrival back in Florida is targeted for 10:30 a.m. EDT on Monday. It will be a straight non-stop shot from Barksdale to the Kennedy Space Center.

"Shuttle managers will meet again with air crews and the weather team at 2 p.m. EDT Saturday to discuss how possible a Sunday morning departure would be and decide the best route to get Discovery back to Kennedy within two days, weather permitting," an agency spokesman says.

Work underway today is focused on getting Discovery mounted atop the 747 carrier aircraft.

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Crews have been working to install the aerodynamic tail cone around the shuttle's engines, plus hydraulic operations to retract the landing gear and set the aerosurfaces for the flight.

Managers will meet again Friday to review the weather outlook and determine the trip's initial path across the country to intermediate refueling stops.

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Ground crews having completed the hazardous draining of fluids and propellants from the shuttle. The main engines were dried and cryogenics from the electricity-generating fuel cells were offloaded as well..

Key work remaining to be completed includes installation of the aerodynamic tail cone onto Discovery and the subsequent hoisting of the shuttle atop the carrier aircraft on Thursday.

Since Discovery landed last Friday at the Mojave Desert military base, technicians have worked through the routine procedures to ready the spacecraft for its voyage home. The shuttle was towed off the runway and positioned within the cocoon-like framework structure known as the Mate/De-Mate device that gives access around the orbiter and does the heavy-lifting to mount the 110-ton craft aboard the 747.

The team includes about 50 locals who work at NASA's Dryden Flight Research Center, plus 65 from Kennedy Space Center who were pre-deployed there in advanced of a possible landing and another 160 KSC employees flown out there after Discovery touched down.

Managers plan a Flight Readiness Review around mid-day on Thursday to plan the ferry timeline and initial path.

Arrival back at the Kennedy Space Center isn't expected before Saturday.

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Additional coverage for subscribers:
VIDEO: SHUTTLE DISCOVERY LANDS IN CALIFORNIA PLAY
VIDEO: BEHIND THE SCENES IN MISSION CONTROL PLAY
VIDEO: LANDING REPLAY: CAMERA 1 PLAY
VIDEO: LANDING REPLAY: CAMERA 2 PLAY
VIDEO: LANDING REPLAY: CAMERA 3 PLAY
VIDEO: LANDING REPLAY: CAMERA LOOKING OUT PILOT'S WINDOW PLAY
VIDEO: NASA AND ESA POST-LANDING BRIEFING PLAY
MORE: STS-128 VIDEO COVERAGE
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Main Gear Touchdown
8:53:25 p.m. EDT
MET: 13 days, 20 hours, 53 minutes, 45 seconds

Nose Gear Touchdown
8:53:34 p.m. EDT
MET: 13 days, 20 hours, 53 minutes, 54 seconds

Wheels Stop
8:54:35 p.m. EDT
MET: 13 days, 20 hours, 54 minutes, 55 seconds

The shuttle will cross above the runway when performing the incredibly wide and sweeping 213-degree right-overhead U-turn to align with Runway 22.