By Joey Roulette

WASHINGTON Virgin Galactic , the space tourism firm founded by Richard Branson, is set to launch its first spaceflight mission in nearly two years on Thursday, a final planned test flight with a crew of six before it kickstarts its long-awaited commercial service.

The company's Unity 25 mission from Spaceport America, New Mexico, comes 22 months after billionaire Branson and other Virgin Galactic employees rode to the edge of space aboard the company's centerpiece SpaceShipTwo spaceplane. That was a high-profile mission it hoped would open the door to routine flights soon after.

But a safety probe into Branson's flight by the U.S. Federal Aviation Administration hampered the company's near-term plans, as did a lengthy spacecraft upgrade period that lasted longer than Virgin Galactic originally anticipated.

Virgin Galactic is now targeting a morning flight window beginning 10 a.m. Eastern time. The twin-fuselage carrier plane, named VSS Eve, will take off from a runway at the New Mexico site carrying the suborbital SpaceShipTwo, named VSS Unity.

If all goes well, Virgin Galactic hopes to fly its first commercial mission in late June, a long-delayed research flight chartered for the Italian Air Force. The company then expects to carry out a mission roughly every month.

Virgin Galactic pilots Jameel Janjua and Nicola Pecile will fly the carrier aircraft VMS Eve and drop the spaceplane when it reaches around 50,000 feet in altitude. The spacecraft, once untethered, will ignite a rocket engine and climb to an altitude in microgravity of roughly 50 miles, the U.S.-recognized boundary of Earth's atmosphere.

The test mission, lasting roughly 90 minutes from takeoff to the spaceplane landing after spending three minutes in microgravity, follows the type of rides Virgin Galactic intends to provide for a backlog of some 800 customers. Most have paid between $250,000 and $450,000 for a ticket.

The company in April conducted a successful glide test with VSS Unity, dropping it at 47,000 feet for a free-fall back to its runway, without having ignited its engine to go toward space.

Mike Masucci and CJ Sturckow will pilot the spaceplane. In the cabin will be the company's chief astronaut instructor Beth Moses, astronaut instructor Luke Mays, senior engineering manager Christopher Huie and Jamila Gilbert, internal communications senior manager.

(Reporting by Joey Roulette; Editing by David Gregorio)