Stratolaunch, a giant six-engine aircraft with the world's longest wingspan , makes its historic first flight from the Mojave Air and Space Port in Mojave, Calif., Saturday, April 13, 2019. Founded by the late billionaire Paul G. Allen, Stratolaunch is vying to be a contender in the market for air-launching small satellites. (AP Photo/Matt Hartman)

A giant six-engine aircraft with the world's longest wingspan completed what company officials called a superb initial flight over California's Mojave Desert, bringing to life a dream held by the late Microsoft co-founder Paul G. Allen.

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.

"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 behemoth, twin-fuselage Stratolaunch jet lifted off from Mojave Air and Space Port shortly before 7 a.m. Saturday and climbed into the desert sky 70 miles (112 kilometers) north of Los Angeles. The jet flew 2 ½ hours, achieving a maximum speed of 189 mph (304 kph) and altitudes up to 17,000 feet (5,181 meters), 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, which stretches 385 feet (117 meters)—a longer wingspan than any other aircraft.

At an altitude of 35,000 feet (10,668 meters), the rockets would be released, ignite their engines and soar into space.

Stratolaunch, a giant six-engine aircraft with the world's longest wingspan , makes its historic first flight from the Mojave Air and Space Port in Mojave, Calif., Saturday, April 13, 2019. Founded by the late billionaire Paul G. Allen, Stratolaunch is vying to be a contender in the market for air-launching small satellites. (AP Photo/Matt Hartman)

The advantages of such air-launch systems include 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, the co-founder of Microsoft, 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.

After Allen's death in October 2018, Stratolaunch dropped plans to develop its own type of rocket engine and a family of launch vehicles, focusing instead on getting the giant plane airborne and launching Northrop Grumman's proven Pegasus XL.

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.

Stratolaunch, a giant six-engine aircraft with the world's longest wingspan , makes its historic first flight from the Mojave Air and Space Port in Mojave, Calif., Saturday, April 13, 2019. Founded by the late billionaire Paul G. Allen, Stratolaunch is vying to be a contender in the market for air-launching small satellites. (AP Photo/Matt Hartman)

Powered by the same type of engines used by Boeing 747s, the aircraft is designed to take off at a maximum weight of 1.3 million pounds (589,676 kilograms). Its twin fuselages—sort of the airplane equivalent of a catamaran—are 238 feet (72.5 meters) long.

The previous wingspan leader was Howard Hughes' World War II-era eight-engine H-4 Hercules flying boat—nicknamed the Spruce Goose. Surviving in an aviation museum, it has an approximately 320-foot (97.5-meter) wingspan but is just under 219 feet (67 meters) long.

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 (84 meters) long, and the Boeing 747-8, which is just over 250 feet (76.3 meters) long.

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