DALLAS (CBSDFW.COM) – There were strange lights above the skies of North Texas on Monday morning — again!

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The Solar Impulse lifted off from DFW International Airport just after 4:00 a.m. Monday morning. There were a few challenges for the pilot as the plane prepared to take off — particularly the weather — but the solar-powered plane managed to get out of the Metroplex just fine.

The plane is now bound for St. Louis, in a flight that is expected to take 21 hours. This is the longest leg of the Solar Impulse’s cross-country mission. When the plane lands, it will be sheltered in a large inflatable hangar at the airport in St. Louis, after the intended hangar was damaged on Friday by severe storms.

The Solar Impulse arrived in North Texas on May 23, as part of a cross-country journey. When the solar-powered plane was landing in DFW during the overnight hours, several people thought that it was a UFO hovering in the sky. The plane began its mission in California and stopped in Phoenix before coming to North Texas.

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After landing in St. Louis, the Solar Impulse moves to Washington, D.C. and finally New York City. The aircraft flies with no fuel at an average speed of 40 mph.

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