Flight Crew Last 90 Days 29; Flight Crew Total 2480; Flight Crew Type 2480
Confusion; Situational Awareness
Ground Event / Encounter Other / Unknown; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Became Reoriented
Human Factors; Procedure
During acft receipt at a fixed jetway the aircraft was determined to be approximately 8 to 12 inches too far forward of the parking mark. Ground crew established verbal contact and coordinated with the cockpit crew to push the aircraft back to the correct spot. After the initial attempt to set the aircraft on the mark; the ground crew communicated that they would have to attempt the movement again and proceeded to tell the Captain to release the brakes. When I released the brakes; the aircraft began moving backwards and after about 1.5 feet; the ground crew said; 'Ground to Cockpit; set brakes'.Then the ground crew advised us that we would have to release the brakes so that he could pull us forward. At this point; I asked the ground crew if we had been attached to the tug when he had previously instructed us to release the brakes. He informed us that we were NOT in fact attached; so we therefore had experienced an uncommanded movement of the aircraft. At this point; the final attempt to bring the aircraft to the parking mark was only undertaken after I specifically inquired as whether the aircraft was secured to the tractor.
[Report narrative contained no additional information.]
Flight Crew reported ground personnel advised them to release brakes when they were not connected to a tug and the aircraft rolled backwards.