The Boeing-built X-37B Orbital Test Vehicle (OTV) shown at Nasa’s Kennedy Space Center in Florida (Credits: AP)

Nasa has had a top secret, unmanned space plane orbiting the planet for the last two-and-a-half years.

Known as X-37B, the craft landed early on Saturday morning after spending a record 908 days in orbit.

This was its sixth consecutive mission and the longest time it has remained in orbit without maintenance.

The solar-powered vehicle, which looks like a miniature space shuttle, landed at Nasa’s Kennedy Space Center.

Its previous mission lasted 780 days.

‘Since the X-37B’s first launch in 2010, it has shattered records and provided our nation with an unrivaled capability to rapidly test and integrate new space technologies,’ said Jim Chilton, a senior vice president for Boeing, its developer.

Technicians approach the space plane following its touch down after 908 days in space (Credits: U S Space Force/UPI/Shutterstock)

Residents of central Flordia were probably a little nonplussed with the space ship’s return. It reportedly caused a sonic boom as it returned to earth that could be heard across the state.

Twitter user Robert Haas, wrote: ‘Woke me up, thought something hit the house, Facebook and Twitter seem to confirm it was what I thought, sonic boom seems likely.’

Another wrote: ‘I heard a triple boom at 5.15am in Haines City, FL. I thought someone jumped on my roof!’ 

‘Just woke up to a sonic boom shaking the house. I’m seeing reports from Tampa to Titusville. What the hell just flew across Florida? Was there a launch?,’ another user wrote. 

‘Just heard a sonic boom in the Orlando area. No launch scheduled right now,’ Matt Collins wrote. 

Sophie Sanchez claimed she ‘saw’ the rocket landing near the Cape early in the morning and said ‘everyone on the road hit their brakes.’ 

‘When I saw [it, I don’t know] what streaked overhead. Meteor? UFO?’ she had wondered. 

It was later confirmed by the US Space Force that the robotic plane had deorbited at 5.22am, causing the sonic boom.

For the first time, the space plane hosted a service module that carried experiments for the Naval Research Laboratory, U.S. Air Force Academy and others.

The module separated from the vehicle before de-orbiting to ensure a safe landing.

Among the experiments was a satellite dubbed the FalconSat-8 that was designed and built by academy cadets in partnership with the Air Force Research Laboratory. It was deployed in October 2021 and still remains in orbit.

Another experiment evaluated the effects of long-duration space exposure on seeds.

‘This mission highlights the Space Force’s focus on collaboration in space exploration and expanding low-cost access to space for our partners, within and outside of the Department of the Air Force,’ said Gen. Chance Saltzman, Chief of Space Operations.

The X-37B has now flown over 1.3 billion miles and spent a total of 3,774 days in space.

MORE : Pieces of Nasa’s destroyed Challenger spacecraft found on ocean floor

MORE : Earth’s ozone layer continues heal in 2022, says Nasa

The top secret X-37B craft has spent a record 908 days in orbit.