The world's largest aircraft by wingspan completed a successful first flight over California's Mojave Desert on Saturday.

The gigantic, six-engine aircraft known as Stratolaunch has a 385-foot wingspan, weighs about 500,000 pounds and is the dream of late Microsoft co-founder Paul G. Allen. The airplane's six Pratt & Whitney engines and 28-wheel landing gear were originally designed for Boeing 747s, according to the company.

Stratolaunch Systems Corp. Chief Executive Jean Floyd said Saturday the aircraft made a "spectacular" landing that was on the mark. Stratolaunch, which was founded by Allen, is vying to be a contender in the market for air-launching small satellites. He died in October.

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"It was an emotional moment for me, to personally watch this majestic bird take flight, to see Paul Allen's dream come to life in front of my very eyes," Floyd told a teleconference briefing.

Floyd said that as the plane lifted off, "I did whisper a 'thank you' to Paul for allowing me to be part of this remarkable achievement."

The twin-fuselage Stratolaunch jet lifted off from Mojave Air and Space Port shortly before 7 a.m. and climbed into the desert sky 70 miles north of Los Angeles. The jet flew for two and a half hours, achieving a maximum speed of 189 mph and altitudes up to 17,000 feet, the company said.

Test pilot Evan Thomas of Scaled Composites LLC, which built the aircraft, said the flight overall was "fantastic" and for the most part the plane flew as predicted.

"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 and climbed out quickly."

Thomas said there were "a few little things that were off-nominal but really for a first flight it was spot-on." He did not specify what those things were, and briefing participants did not take questions.

The aircraft is designed to carry as many as three satellite-laden rockets at a time under the center of its enormous wing.

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Air-launch systems have a number of advantages, including being able to use numerous airports and avoid the limitations of fixed launch sites which can be impacted by weather, air traffic and ship traffic on ocean ranges.

Allen founded Stratolaunch Systems Corp. in 2011 after emerging in aerospace by funding the development of the experimental air-launched SpaceShipOne, which in 2004 became the first privately built manned rocket to reach space.

The Stratolaunch aircraft emerged from its Mojave hangar for the first time in May 2017 and proceeded through ground tests, including taxiing and rolling down a runway at near-takeoff speeds.

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While Stratolaunch calls its aircraft the world's largest, other airplanes exceed it in length from nose to tail. They include the six-engine Antonov AN 225 cargo plane, which is 275.5 feet long, and the Boeing 747-8, which is just over 250 feet long.

The Associated Press contributed to this report.