Update 12:57 p.m. EDT: Richard Branson and the Unity 22 crew have safely landed back at Spaceport America. Read the full story here. A post-flight press conference is about to begin shortly, and you can watch it live in the window above.
Update 11:29 a.m. EDT: "Welcome to space, Unity 22," Virgin Galactic says as SpaceShipTwo VSS Unity successfully performed a full-duration burn, launching its crew above the 50-mile marker used by NASA, FAA and U.S. military. Re-entry now underway. Update 11:21 am EDT: Virgin Galactic reports VSS unity is L-4 minutes from launch.
Update for 10:58 a.m. EDT: The carrier plane VMS Eve and the VSS Unity spaceplane are currently cruising up to launch altitude. Unity drop and motor ignition is expected at 11:20 a.m. EDT (1520 GMT). See how Virgin Galactic's astronauts arrived at Spaceport America today for launch here.
Update for 10:45 a.m. EDT: Virgin Galactic's Unity 22 launch webcast has begun.
Virgin Galactic will launch its billionaire founder Richard Branson and a crew of five others into suborbital space today (July 11) and you can watch milestone flight live online.
The 70-year-old Branson and the rest of his Unity 22 mission's crew will depart from Spaceport America about 55 miles (88 kilometers) north of Las Cruces, New Mexico on Virgin Galactic's VSS Unity SpaceShipTwo vehicle. The live broadcast was originally scheduled to start at 9 a.m. EDT (1300 GMT), but will now begin 90 minutes later at 10:30 a.m. EDT (1430 GMT) due to weather delays moving the SpaceShipTwo VSS Unity and it's carrier plane VMS Eve out of their hangars, Virgin Galactic said today.
You'll be able to watch the broadcast live on this page, the Space.com homepage and directly from Virgin Galactic (opens in new tab). The Late Show's Stephen Colbert will host Virgin Galactic's webcast, with singer Khalid performing a new single and science communicator Kellie Gerardi, who will launch on a SpaceShipTwo flight next year, also appearing. Former Canadian Space Agency astronaut Chris Hadfield will, too.
Related: What to know about Virgin Galactic's SpaceShipTwo Unity 22 launch
More: How Virgin Galactic's SpaceShipTwo works (infographic)
Virgin Galactic has also now released key timing milestones of the flight.
Branson and his fellow Unity 22 crew, six people in all (two pilots, four passengers) will walk out to their vehicles about an hour before takeoff. The engines on VMS Eve will be switched on about 30 minutes before the webcast begins.
About 50 minutes after the webcast begins, (about 11:20 a.m. EDT, or 1520 GMT), VMS Eve is expected to release Unity from an altitude of about 50,000 feet (15,000 meters). Unity will ignite its rocket motor and launch on its spaceflight while its carrier plane pulls away.
Unity will land at Spaceport America about 1 hour, 5 minutes after takeoff, about 11:35 a.m. EDT (1535 GMT), according to Virgin Galactic's timeline.
Related: The long road to spaceflight for Virgin Galactic and Blue Origin
Based on past Unity flights, Sunday's mission will last about 90 minutes in total, and the "weightless" phase — when the ship reaches the top of its suborbital path — will last about four minutes.
Branson's fellow passengers will include Beth Moses, Virgin Galactic's chief astronaut instructor; Colin Bennett, Virgin Galactic lead operations engineer; and Sirisha Bandla, the vice president of government affairs and research operations at the company. VSS Unity will be piloted by Dave Mackay and Michael Masucci, with C.J. Sturckow and Kelly Latimer piloting VMS Eve.
If all goes to plan, Branson is expected to achieve spaceflight only nine days before another company, Blue Origin, notches a similar milestone with its New Shepard suborbital vehicle. Blue Origin expects to send its chief — Jeff Bezos, the billionaire Amazon founder who recently resigned as the e-shopping giant's CEO at age 57 — into space on July 20, along with a small crew.
In Photos: Virgin Galactic's Sleek Under Armour Spacesuits for Space Tourists
Bezos' flight will come on the 52nd anniversary of the first crewed moon landing, that of Apollo 11, in 1969. Branson has said in interviews that he was inspired to go to space as a young man after watching the moonwalkers' mission. More recently, Branson denied that he and Bezos are in competition to get to space first; Bezos has remained largely silent on the matter.
Technically speaking, whether a successful flight will actually reach space depends on the definition you use. SpaceShipTwo flights typically fly slightly below the Kármán line, the 62-mile (100 kilometers) altitude mark recognized by many people as the boundary of space. But VSS Unity has already flown three crewed test missions above 50 miles (80 km), the demarcation line recognized by NASA, the U.S. military and the U.S. Federal Aviation Administration.
Virgin Galactic has been aiming to bring tourists into space since its foundation in 2004, while Blue Origin has been trying for the same after its foundation four years earlier. The SpaceShipOne vehicle, on which Virgin Galactic based the design of SpaceShipTwo, flew 62.5 miles (100 km) above Earth's surface twice in 2004 to win the $10 million Ansari X Prize for repeated flights in a privately developed, reusable spacecraft.
Unity 22 will be Virgin Galactic's fourth crewed spaceflight, while Bezos will be aboard the first crewed spaceflight for Blue Origin (though New Shepard has aced more than a dozen uncrewed suborbital test flights). The most recently stated price for a Virgin Galactic seat was $250,000, and more than 700 people have put down a deposit, company representatives have said.
Blue Origin has not yet released its per-seat pricing, although a so-far anonymous auction winner paid $28 million to fly to space on July 20 with Bezos, his brother Mark and Mercury 13 aviator Wally Funk.
Visit Space.com Sunday, July 11, for complete coverage of Virgin Galactic's SpaceShipTwo launch with Richard Branson.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.