The Space Gyro's are the ships of the Lion Men.
In the comic strip, "a squadron of deadly Space-Gyros" attack Ming's palace. Flash Gordon, desperate to save Dale Arden, pilots a rocket ship and shoots down the lead ship. Another ship shoots "gas rays" at Flash, forcing him down for a crash landing. Ming's guards take care of the rest. ("Flash Gordon (comic strip)")
The ships are called Space-Gyros in the first two strips, and become Space Gyros in the third. The non-hyphenated spelling continues on April 15-22.