This morning, Virgin Galactic conducted the second powered flight test of its spaceplane, the VSS Unity, over the Mojave Desert just 54 days after the company ignited the vehicle’s engine for the first time during flight. It marks another successful in-flight engine burn for the spacecraft, nearly four years after a previous version of the vehicle fatally crashed. With each new test, Virgin Galactic gets closer to sending paying customers to space.

Unlike most launch vehicles that take off from the ground, Unity is designed to take off from under the wing of a giant white airplane. Today, the carrier aircraft, known as WhiteKnightTwo, took off from Virgin Galactic’s facilities at Mojave Air and Space Port with the spaceplane in tow. The giant plane hoisted the Unity to a height of 45,600 feet before releasing it into the atmosphere. From there, the vehicle’s engine ignited, carrying the spaceplane’s two pilots — Dave Mackay and Mark “Forger” Stucky — to nearly 22 miles above the Earth’s surface and reaching a top speed of Mach 1.9, which is nearly twice the speed of sound. During its first powered flight, Unity reached Mach 1.87 and an altitude of nearly 16 miles.

For today’s flight test, VSS Unity’s engine burned for just 31 seconds, which is shorter than the 60 seconds it would burn during a normal flight. That’s because the main goal was to see how the plane handled traveling at supersonic speeds with more weight in its rear. After the last powered flight, Virgin Galactic added more passenger seats and extra equipment to the back of Unity, changing the vehicle’s center of gravity. Once the engine burn was over, the pilots shifted the position of the spaceplane’s wings — a process known as feathering — to safely descend through the atmosphere and land on a runway.

“It was great to see our beautiful spaceship back in the air and to share the moment with the talented team who are taking us, step by step, to space,” Virgin Galactic CEO Richard Branson said in a statement. “Seeing Unity soar upwards at supersonic speeds is inspiring and absolutely breathtaking. We are getting ever closer to realizing our goals.” 

So far, Virgin Galactic has safely pulled off two powered flights, and seven successful glide flights, during which the spaceplane flew on its own but its engine wasn’t on. It’s been a fairly successful test program for Unity so far. And with each new powered test flight, Virgin Galactic further distances itself from the 2014 crash. During that test, a previous version of Unity broke apart when its wings shifted too early during the powered portion of the flight. The failure caused the death of one test pilot, while a second pilot was severely injured.

Virgin Galactic says it will look over the data from today’s flight as it preps for the next powered test. It’s still unclear how many more powered flights Virgin plans to do before putting paying customers on board. Branson recently told BBC Radio that he plans to fly into space soon with the company, and flights to space are “months away, not years away.” However, Virgin Galactic has refrained from setting firm dates for its first paying customers.

The company already has hundreds of customers signed up to take a flight on Unity for $250,000 a ticket. Once it becomes operational, the spaceplane is meant to take people to the edge of space, where they’ll experience a few minutes of weightlessness before heading back to Earth.