Built by rocket launch company Stratolaunch, the 500,000-pound plane with a 385-foot wingspan lifted off shortly after 10AM ET from Mojave Air and Space Port in Mojave, California. It’s a critical first test flight for the aircraft, designed to launch rockets into orbit from the air.

WOW. First flight of the worlds largest airplane. History is made. @Stratolaunch @NASASpaceflight #stratolaunch pic.twitter.com/e7x0omxvVc

— Jack Beyer (@thejackbeyer) April 13, 2019

The inaugural flight is expected to last a few hours. The dual-fuselage Stratolaunch is designed to fly to an altitude of 35,000 feet, where it can drop rockets that ignite their engines and boost themselves into orbit around the planet. There is no rocket on this particular flight. But the company has already signed at least one customer, Northrop Grumman, which plans to use Stratolaunch to send its Pegasus XL rocket into space.

The aircraft’s wingspan measures 385 feet — wider than any airplane on the planet. From tip to tail, it’s 238 feet long. It weighs half a million pounds. It’s so big, it has two cockpits, one in each fuselage (but only one is used to fly the plane.)

The company’s unique air-launch system will use the world’s largest aircraft as a mobile launch platform, capable of deploying launch vehicles that will carry satellites to multiple orbits and inclinations on a single mission. With these new vehicles, Stratolaunch is poised to make access to space convenient, affordable, and routine.

The updated launch offering from Stratolaunch includes the following vehicles:

• Pegasus: With its existing track record of over 35 successful launches, Pegasus provides dependable access to orbit.
• • Capability: 370 kg payload* for a single or triple configuration
• • Status: Flight proven, integration and testing ongoing with first flight in 2020
• Medium Launch Vehicle (MLV): A new medium-class air-launch vehicle optimized for short satellite integration timelines, affordable launch and flexible launch profiles.
• • Capability: 3,400 kg payload*
• • Status: In development with first flight in 2022
• Medium Launch Vehicle – Heavy: A three-core MLV variant with capability to deploy heavier payloads to orbit.
• • Capability: 6,000 kg payload*
• • Status: Early development
• Space Plane: A fully reusable space plane that enables advanced in-orbit capabilities and cargo return. Initial designs optimized for cargo launch, with a follow-on variant capable of transporting crew.
• • Capability: Medium-class payload or crew
• • Status: Design study