CAPE CANAVERAL, Fla. (AP) — The U.S. military’s mystery space plane rocketed into orbit again Sunday, this time with an extra load of science experiments.

It’s the sixth flight of an X-37B, a solar-powered plane that's flown by remote control without a crew. Officials aren't saying how long the spacecraft will remain in orbit this time or the purpose of the mission.

The previous mission lasted a record two years, with a touchdown shrouded in darkness at NASA's Kennedy Space Center last year.

The winged spacecraft resembles NASA’s old shuttles, but is considerably smaller at 29 feet long. The one just launched features an extra compartment for experiments, including several for NASA. The Air Force has two of these reusable space planes.

Since the first flight in 2010, the space planes had logged a combined 2,865 days in orbit as of Sunday. That's seven years and 10 months.

Delayed a day by bad weather, this marks just the second rocket launch for the newly established Space Force. In March, it hoisted a national security satellite.

United Launch Alliance, which provided the Atlas V rocket, dedicated Sunday's launch to the health care workers and others who are working on the front lines of the pandemic.

The company said it followed health advice for the launch. Many of the flight controllers wore masks and were spread out.

The Cape Canaveral Air Force Station has an exceptionally fast turnaround for its next launch.

Before dawn Monday, SpaceX will attempt to launch another batch of its Starlink satellites for global internet service. It will be SpaceX's last flight before its first astronaut launch, scheduled for May 27 from next-door Kennedy Space Center.

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