Commander Mark Kelly and his co-pilot fired the braking rockets to begin the hourlong descent from orbit. Endeavour was due to touch down at 2:35 a.m. EDT.
Meanwhile, Atlantis slowly made its way to the launch pad for the last shuttle flight, coming up in just five weeks. Atlantis crept out of the mammoth Vehicle Assembly Building a little after sunset, bathed in xenon lights. Thousands of Kennedy Space Center workers and their families gathered to see Atlantis make its way to the pad.
"The show pretty much tells itself," Atlantis' commander, Christopher Ferguson, said as he waved toward his ship. "We're going to look upon this final mission as a celebration of all that the space shuttle has accomplished over its 30-year life span."
Kelly and his crew were eager to get home and hand the spotlight over to the Atlantis crew.
"Endeavour's performed really, really well for us over these 16 days, as it has since its first flight," Kelly said.
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 will blast off on the final flight ever by a shuttle July 8. The three-mile trip from the hangar — the beginning of it lined with the cars of space center workers seeking a front-row view — should be completed soon after Endeavour lands.
It will be just the 25th time NASA has brought a space shuttle back to Earth in darkness — representing less than one-fifth of all missions.
All four astronauts assigned to Atlantis' flight were on hand for the historic double-header.
"Look how majestic it looks rolling out to the launch pad," said Atlantis astronaut Sandra Magnus. "It's really hard to say goodbye to the program. But on the other hand, look at the great things that we've accomplished and look at what we can do with that in the next era."
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 Endeavour 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, remained at her rehab center in Houston. She traveled to Kennedy for the launch, but the landing time was 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.
Endeavour is the second shuttle to be retired; it ultimately will be at the California Science Center in Los Angeles. Discovery ended its last voyage in March; its final destination is a Smithsonian Institution hangar outside Washington. Atlantis will remain at Kennedy Space Center as a tourist stop.
NASA is leaving the Earth-to-orbit business behind to focus on expeditions to asteroids and Mars. Private companies hope to pick up the slack for cargo and crew hauls to the space station.