Atlantis crept out of the mammoth Vehicle Assembly Building a little after sunset. At 2:35 a.m. Wednesday, Endeavour was due to touch down on the shuttle landing strip just a few miles away.
Thousands of Kennedy Space Center workers and their families gathered to see Atlantis make its way to the launch pad for the final time in the 30-year shuttle program.
Circling more than 200 miles overhead, Mark Kelly and his crew were eager to get home.
"Endeavour's performed really, really well for us over these 16 days, as it has since its first flight," Kelly said from orbit as his mission drew to a close.
"When we land in Florida tomorrow, it's going to roll into the hangar and get prepared for the next step, the next phase of its life, which is in a museum. I imagine millions of people, hopefully millions of people a year will get to enjoy getting up close to the space shuttle ... but it is a bittersweet moment, it's been a great spacecraft."
Endeavour left the International Space Station over the weekend. The astronauts put the finishing touches on the orbiting lab, installing a $2 billion cosmic ray detector, an extension beam and a platform full of spare parts - enough to keep the station operating in the shuttle-less decade ahead.
Atlantis, meanwhile, will blast off on the final flight ever by a shuttle July 8. The three-mile trip from the hangar - much of it lined with the cars of space center workers seeking a front-row view - should be completed soon after Endeavour lands.
All four astronauts assigned to Atlantis' flight were on hand for the historic double-header.
Flight director Tony Ceccacci said the landing weather looks "very promising." For the first time in days, the crosswind forecast is within safety limits. The rules are stricter for nighttime landings.
It will be the 25th time NASA has brought a space shuttle back to Earth in darkness - representing just one-fifth of all missions.
Endeavour will have traveled 123 million miles by flight's end - on all 25 of its voyages - and spent 299 days in space. It's the youngest of NASA's shuttles, first flying in 1992 as the replacement for Challenger.
In a series of TV interviews late Monday, the astronauts talked about how huge and spectacular the space station has become. It's so sprawling that it barely fits in the shuttle viewfinder from 600 feet out, pilot Gregory Johnson said.
And as has become the custom, Kelly fielded numerous questions about his wife, Rep. Gabrielle Giffords.
Giffords, who's recovering from a gunshot wound to the head, will remain at her rehab center in Houston. She traveled to Kennedy for both launch attempts, but the landing time is too inconvenient to warrant another trip, her husband said.
On Monday, she had the stitches removed from the skull reconstruction that she underwent just two days into his flight. Kelly said he'll call her as soon as he lands - he expects his first words to be "I'm back" - and embrace her once he returns to Houston the day after touchdown.
Kelly said he has no regrets about having made the flight. He took a leave from NASA when the shooting occurred Jan. 8 in Tucson, Ariz., and for a while thought he might have to quit. But Giffords improved so much that when Kelly moved her to Houston for rehabilitation, he resumed flight training.
"In hindsight, it was absolutely the right decision," Kelly said. That's evidenced by the fact that the crew met all of its objectives in orbit: installing the Alpha Magnetic Spectrometer, carrying out four spacewalks, wrapping up the U.S. portion of space station construction.
"Being away from her, to be honest, it's difficult," he said.
But it was "really, really special" that she could make the trip to Cape Canaveral - twice - given everything that happened to her. Endeavour is the second shuttle to be retired. Discovery ended its last mission in March.