Virgin Spaceship Unity and Virgin Mothership Eve take to the skies on it's first captive carry flight on September 8, 2016 (photo courtesy of Virgin Galactic)

Virgin Galactic, the company founded by Richard Branson to ferry tourists to space, returned to flight this week nearly two years after its spacecraft came apart during a test flight, killing one of the pilots.

Cruising over the Mojave desert for three hours and 43 minutes, a mothership ferried SpaceShipTwo to an altitude of about 50,000 feet in what the company called “an exciting milestone in our shared quest to open space to change the world for good.”

Unlike the rockets used by NASA that launch vertically from a launch pad, Virgin “air launches” its spacecraft. They are tethered to the belly of a large airplane, which carry them into the sky. The spacecraft then drops, fires its engines and soars to a suborbital altitude.

During Virgin’s test, the spacecraft stayed connected to the carrier plane the entire time.

Virgin is hoping to be the first company to fly tourists just past the edge of what’s considered space. It has hundreds of people signed up for the flights, some of whom have paid as much as $250,000. But another space company founded by Amazon.com founder (and Washington Post owner) Jeffrey P. Bezos is also developing rockets designed to fly tourists into space.

The company, Blue Origin, said this week that it plans to perform a key test next month that would bring those flights closer to reality. It plans to launch its New Shepard rocket at its test site in west Texas, and then perform what’s known as an in-flight escape: the capsule that would hold the passengers would blast away from the booster, and land at a safe distance away under parachutes.

It’s an important maneuver designed to keep astronauts safe in case anything happens to the rocket. In a statement, Bezos said the “upcoming flight will be our toughest test yet’’—one that he said would probably end up destroying the booster. See an animation of it here:

Blue Origin's New Shepard rocket has an escape system that can quickly propel the crew capsule to safety if a problem is detected with the booster. (Blue Origin)

The New Shepard rocket made history when it became the first rocket to pass the 60-mile high threshold of space and then land so that it could be reused. Most rockets are discarded after a single use, but recovering them so that they can be reflown is a key step toward lowering the cost of spaceflight. SpaceX has been pulling off similar feats, but with larger, more powerful rockets, capable of reaching orbit.

So far, New Shepard has flown four times—all without passengers. If the rocket somehow survives this flight, Bezos said the company would “reward it for its service with a retirement party and put it in a museum.”

It’s more likely, however, that the booster won’t survive, he said. And since it would still have most of its fuel, it could set off quite an explosion.

“Our next flight is going to dramatic,” he wrote, “no matter how it ends.”

Bezos has said that test flights with crews could start next year, with the first ticketed passengers flying as soon as 2018.

Virgin’s first tourist flights have been repeatedly postponed, and the company now says it will fly only after its vehicles have completed a rigorous flight testing schedule. In 2014, an earlier version of its SpaceShipTwo vehicle blew apart, killing the co-pilot, Michael Alsbury.

This week’s flight was the first time Virgin’s new vehicle, dubbed Unity, had taken to the skies. It was “an emotional and fulfilling moment for our hardworking team, even as we recognize how much work we have yet to do,” the company said. “With this flight in the books, our team will now analyze a mountain of flight data, learning what worked well and what could be improved for our next flight test.”

Read more:

The inside story of how billionaires are racing to take you to outer space

The vehicles that will take you to space

Jeff Bezos pulls back the curtain on his plans for space

Richard Branson's Virgin Galactic unveils new spacecraft, 'Unity'