On 12.30.2022, the FBI released its latest batch of declassified files on the hijacking of Flight 305 on 11.24.1971: "D.B.Cooper Part 78". On pages 85-86 we read: "“... during the hijacking the comment was made by the hijacker concerning IFR clearance, "you can pick it up in the air."” The hijacker was apparently aware of FAA AIM para. 4.4.9, or its equivalent in 1971 (if an equivalent existed then). In 2023, 4.4.9 states: "VFR/IFR Flights: A pilot departing VFR, either intending to or needing to obtain an IFR clearance en route, must be aware of the position of the aircraft and the relative terrain/obstructions." Could any pilot say what level of aeronautical knowledge and/or experience (as of the year 1971) is implied by the hijacker's statement?