A mysterious NASA plane has been spotted in eastern Africa, leaving people curious whether it was on some secret mission.

The broad-winged white plane named WB-57 was photographed by the satellite company Digital Globe in the Republic of Djibouti in September, ABC News reported.

“I really cannot give you any of the details. You know the airplane was there, you see it in the picture. But I really can’t tell you what it was for,” Jim Alexander, a NASA official with the WB-57 High Altitude Research Programme, told ABC News.

According to the space agency, all three WB-57s are now back in the US with their status listed as “inactive”.

According to NASA’s website, the WB-57s have been flying research missions “since the early 1970s and continue to be an asset to the scientific community with professional, reliable, customer-oriented service designed to meet all scientific objectives”.

The plane can fly nearly as high as the famed U2 spy plane and carry more weight – including an array of high-tech imagery and communications equipment, the report added.

The WB-57 can carry any number of sensor payloads.