"JAFO" is Airforce/Navy derogatory slang for an Observer [co-pilot]. [The movie "Blue Thunder" with Roy Scheider made reference to the term].
I've worked as an FIA Observer[communications] Official at the Australian Grand Prix for the past 24 years [and the 500 Motorcycle Grand Prix], not to mention the first Nascar race outside the U.S., hence the name.
BTW, JAFO = Just Another F***ing Observer.
[PPL only ever seem to be aware of the Trackside Flag Marshals, and any other Trackside Officials go un-noticed.]...