NEW YORK, April 23, 2012 — The countdown for space shuttle Enterprise's touchdown in New York is back on.

The prototype NASA orbiter, which never flew in space but was used by the space agency for approach and landing tests in the late 1970s, will now take off from Washington, D.C. for the Big Apple on Wednesday (April 25), pending a final review of the weather on Tuesday.

The Federal Aviation Administration (FAA) is coordinating the flight, which is scheduled to occur between 9:30 and 11:30 a.m. EDT (1330 and 1530 GMT). The exact route and timing depend on weather and operational constraints.

Later this summer, Enterprise will be transported by barge to New York's Intrepid Sea, Air & Space Museum, on the retired World War II aircraft carrier USS Intrepid, for public display.

NASA's original prototype orbiter had been scheduled for delivery to John F. Kennedy (JFK) International Airport on Monday (April 23) but concerns over the weather delayed its departure. NASA managers met on Monday afternoon to reassess the forecasts and set the new date.

Space shuttle Enterprise awaits its last flight atop NASA's Shuttle Carrier Aircraft, now scheduled for (NASA / Bill Ingalls)

Enterprise had been exhibited in the Smithsonian National Air and Space Museum's Steven F. Udvar-Hazy Center in Chantilly, Va., since 2003, but was displaced when the space-flown shuttle Discovery arrived last Thursday. The next day, Enterprise was mounted atop the Shuttle Carrier Aircraft, a modified Boeing 747 jumbo jet, and has since sat at Washington Dulles International Airport waiting for sunny skies.

Rain, rain go away

NASA, in consultation with Intrepid officials, announced the flight delay on Friday. Local forecasts called for a low pressure system on the east coast to deliver low clouds and rain in both the Washington and New York areas, precluding the ferry flight begin until Wednesday (April 25) at the earliest.

Over the weekend, rain did fall on Enterprise.

To protect against the showers, shuttle engineers installed makeshift "rain covers" over Enterprise's vent openings on Saturday. After a trip to the local hardware store, workers fabricated the covers out of foam board that they then covered in their hotel parking lot with aluminum sheeting, weather stripping and wood.

The covers will be removed before Enterprise departs for New York.

NASA stated that the decision to delay Enterprise's ferry was to ensure a safe flight for both the test orbiter and the carrier aircraft crew. At the speed they fly, raindrops can inflict damage on the shuttle's heat shield tiles, and due to weight constraints, the jet does not have the fuel reserves to maneuver around the storms.

NASA also hoped to fly Enterprise over some of New York City's landmarks, including low passes near the Statue of Liberty and the Intrepid museum, for photo opportunities. These flyovers however, were weather dependent.

27 years and counting

The last time Enterprise took to the air was on Nov. 18, 1985, when it arrived at Dulles Airport from the Kennedy Space Center in Florida to be donated to the Smithsonian. As with this upcoming flight, it was then mounted on the same aircraft that began its airborne service to NASA.

Before the space-worthy orbiters could fly and return from space, Enterprise flew a series of approach and landing test (ALT) flights in 1977 to verify the shuttle's handling as an unpowered glider when returning from space. Two pairs of two astronaut pilots each flew Enterprise to landings at Edwards Air Force Base in California after the orbiter was lofted to altitude by the Shuttle Carrier Aircraft NASA 905.

For this week's flight, Enterprise will fly without a crew — its own cockpit stripped of its instruments long ago — and will remain mounted to the 747 through the touchdown at JFK in front of an invited audience of 1,500 people.

Rendering of space shuttle Enterprise as it'll be displayed on the flight deck of the Intrepid Sea, Air & Space Museum. (Intrepid)

On the ground, the air- and spacecraft will remain together until NASA can re-stage the large cranes it used to hoist Enterprise atop the jet in Washington to New York.

Enterprise will then wait in a JFK hangar until June, when it will loaded onto a barge and moved around Manhattan to the Intrepid. There, the orbiter will be craned onto the flight deck for display.

The Intrepid's new "Space Shuttle Pavilion," a temporary climate-controlled steel-and-fabric structure, is targeted to open to the public in mid-July.

Visit shuttles.collectspace.com for continuing coverage of the delivery and display of NASA's retired space shuttles.