"It was an emotional moment for me, personally, to watch this majestic bird take flight", Stratolaunch CEO Jean Floyd said in a phone call with reporters.
Built by Stratolaunch, the company set up by the late Microsoft co-founder Paul Allen in 2011, the aircraft is created to act as a flying launch pad for satellites. Stratolaunch, which was founded by Allen, is vying to be a contender in the market for air-launching small satellites. According to Allen, who died October 15, 2018, this system would make satellite launches much easier and faster. "Even though he wasn't there today, I did whisper a 'thank you".
Called Roc, the plane took off at 6:58 a.m. PDT (13:58 GMT) and flew for two and a half hours, reaching an altitude of 5,180m and a full speed of 304 km/h, a statement from Stratolaunch said.
The behemoth, twin-fuselage Stratolaunch jet took off from Mojave Air and Space Port and climbed into the desert sky 112 kilometres north of Los Angeles.
The plane reached speeds of 189 miles per hour (304 km/h) and performed several flight control maneuvers, including "roll doublets, yawing maneuvers, pushovers and pull-ups, and steady heading side slips", the manufacturer Stratolaunch said in a statement.
"The airplane very nicely, smoothly rotated and really just lifted off the ground", he said. "It definitely was ready to fly and wanted to fly", he said.
Thomas said there were "a few little things that were off-nominal but really for a first flight it was spot-on". It must theoretically be used to carry and drop at altitude a small rocket that will then light its engine, and will propel to space to place satellites in orbit. According to the company, the Stratolaunch has a max takeoff weight of 589,670 kilograms and will one day assist in the launching of rockets - and satellites - into space.
The test flight came after a series of taxi tests of the plane at increasing speeds, culminating with one January 10 where the plane's nose gear briefly left the ground.
Powered by the same type of engines used by Boeing 747s, the aircraft is created to take off at a maximum weight of 1.3m pounds. Its twin fuselages - sort of the airplane equivalent of a catamaran - are 238 feet (72.5 meters) long.
The previous wingspan leader was Hughes' second world war-era eight-engine H4 Hercules flying boat, which was nicknamed the Spruce Goose.
Stratolaunch has a wingspan of 386 feet (118 m) and is 26 feet (8 m) long.
Powered by six Boeing 747 engines, the plane is meant to climb twice as high, and with a space rocket strapped underneath.