CAPE CANAVERAL, Fla. — Nearly four months late - and held up by a last-minute computer glitch - space shuttle Discovery blasted off under clear blue skies Thursday afternoon on its final mission to the International Space Station before it is retired next month.

The 27-year-old orbiter, with a crew of six astronauts, thundered from the launch pad at Kennedy Space Center at 4:53 p.m. as tens of thousands of spectators cheered NASA's oldest and most-traveled shuttle.

"The final liftoff of Discovery," exulted Mike Curie, NASA's launch commentator, "a tribute to the dedication, hard work and pride of America's space shuttle team."

It was the 39th liftoff for Discovery, commanded by space veteran Steve Lindsey, a retired Air Force colonel, on an 11-day mission ferrying supplies and a humanoid robot to the International Space Station.

The launch marks the beginning of the end of the U.S. space shuttle program, 30 years after NASA began launching reusable, do-all spaceships into orbit to do everything from launching satellites to building the space station itself. Two more shuttles await their final launches: Endeavour in April and Atlantis as early as June.

Thursday's launch was delayed by a little more than three minutes by a computer glitch experienced by the Range Safety Officer, who assures that the Atlantic Ocean downrange from KSC is clear of ship and airplane traffic. Lift-off occurred with two seconds to spare before the launch window closed.

Throngs of people watched the launch from vantage points all along the Space Coast. Among those in the VIP area were Florida Gov. Rick Scott, watching the first launch since he took office in January, as well as U.S. Sen. Bill Nelson and NASA Administrator Charlie Bolden.

In addition to Lindsey, 50, a fighter pilot who flew dozens of missions in Iraq, the crew includes pilot Eric Boe, 45, an Air Force colonel and fellow fighter-pilot veteran; and mission specialists Alvin Drew, 47; Michael Barratt, 51, a medical doctor; Nicole Stott, who lived on the Space Coast for many years while working as a mission engineer at Kennedy Space Center; and Steve Bowen, 47.

Bowen replaced Tim Kopra, who was injured in a mid-January bicycle accident. Bowen flew aboard Atlantis last May and will be the first astronaut to fly on consecutive shuttle missions.

The highlight of the mission will be delivery of Robonaut 2, otherwise known as R2, a 40-inch robot built by General Motors that looks like a human from the torso up, with capabilities to one day be an active member of the space station crew.

R2 will spend the next year or so attached to a stand in the U.S. lab on the space station, simply being tested in zero-gravity and doing such things as turning knobs, plugging things in and other simple manipulation tasks.

But its long-term prospects - including doing actual work in the space station and even outside it in space - are being eagerly anticipated by NASA and robotic engineers all over the world.