note that while "pathfinder" is referred to as ov-098, she should not be confused with mpta-098 - the main propulsion test article, a steel frame (looking nothing like an orbiter) used to test the space shuttle main engines. "pathfinder" was originally a "fit check" unit, a simple mockup resembling the production orbiters in size, shape and weight, intended to be used to ensure that ground handling facilities would be sized to handle orbiters. she was later rebuilt to resemble them cosmetically, and is currently on display with the external tank used during the propulsion tests (designated mpta-et). to further add to the confusion, it appears that "pathfinder" was never formally numbered, and the ov-098 designation is both unofficial "and" retroactive. mpta-098 was later rebuilt into the shuttle-c mockup during the 1990s; it is currently in storage at the stennis space center.