Endeavour blazed a path through the sky here at the Kennedy Space Center at 8:56 a.m. EDT (1256 GMT), lifting off from the seaside Launch Pad 39A. The shuttle and its six-man crew are bound for the International Space Station, where they will spend 16 days delivering spare supplies and an ambitious astrophysics experiment. [Photos: Shuttle Endeavour's Final Mission]

"Looks like a great day to launch Endeavour for the final time," launch director Mike Leinbach told the crew. "On behalf of thousands of proud Americans who've been part of the journey, good luck, godspeed, see you back here on June 1."

The moment was bittersweet for the thousands of NASA workers who have devoted years to the maintenance of Endeavour and its two sister orbiters. After today, NASA has only one more shuttle mission planned before the shuttles are retired for good.

"Endeavour has had a pretty amazing career," Endeavour's commander Mark Kelly said after he and his crew arrived in Florida for a first launch attempt in April. "It's going to be Endeavour's 25th flight, and me and my crew are excited to be a part of it."

That earlier launch try was called off when a heater used to protect a critical power unit on the shuttle failed just hours before liftoff. Engineers traced the problem back to a switchbox feeding power to the heater. They replaced the box and about 20 feet of wiring connected to it, and conducted thorough tests to make sure the problem was resolved. There were no issues with the system during today's launch countdown.

Kelly is leading a veteran crew of six, including pilot Gregory H. Johnson and mission specialists Mike Fincke, Greg Chamitoff, Andrew Feustel, and European Space Agency astronaut Roberto Vittori.

"I am really excited and charged up for this mission!" Johnson wrote on Twitter this morning.

The launch was witnessed by a crowd of about 500,000 spectators, which included Kelly's wife, Congresswoman Gabrielle Giffords, D-Ariz. Giffords has been recovering in Houston after being shot in January during a community outreach event outside a Tucson, Ariz., grocery store.

After the shooting, Kelly took time off to be with his wife and family, but decided in early February to resume training with the crew and continue as commander of the mission. [Shuttle Endeavour By The Numbers: NASA's 19-Year-Old Space Baby]

"On behalf of all of us, we all know Mark's been through a lot the past few months," Chamitoff said after the crew flew in to Kennedy Space Center last week. "He's done an incredible job keeping track of all the details of this mission. I flew with him on STS-124, he's truly an amazing commander, and all of us feel really, really lucky to have him guide us through this complex mission."

Other notable attendees at the launch included astronaut Mike Collins, who flew on the first manned moon landing mission Apollo 11, five members of Congress, and officials from Italy, Japan, Ukraine, Israel and Bermuda.

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