NASA Photo ID: S79-30357
Date Taken: 03/31/79

Astronaut Robert L Crippen, having just donned a Shuttle spacesuit, experiences a few moments of zero gravity aboard a KC-135 aircraft. Astronaut John W Young, left background (hands to his side), crew commander for STS-1, and Crippen, STS-1 pilot, simulated donning and doffing of the extravehicular mobility suit (EMU) or new hard torso Shuttle suit seen here. Note the foot restraint in which Crippen has his feet planted. This aircract can provide a valid simulation of the weightlessness of space by flying a series of parabolic curves. Note the stand in the background to which the life support system/hard torso combination had been attached for the donning exercise. In actual Shuttle flights, the top part of the spacesuit and its connected life support system will be mounted similarly to the airlock well.

Source: NASA photo in my possession