In my opinion, the sightings were (mostly) real and were a natural+unnatural phenomena due to the exhaust from powerful aircraft engines. The exhaust from these engines contained unburt fuel, a good amount of soot (carbon particulates), and a zoo of small-to-medium molecular weight hydrocarbons created in the cylinder. (Catalytic converters were not standard equipment, back then.) The "glowing" was, IMO, due to actual slow "burning" (oxidation) of this nasty stuff. Each engine could put 5-8 pounds (2-4 kg) of exhaust in the stream per minute if buring 50-70 gallons of fuel per hour/engine. The "ethereal" nature of the phenomena would make it seem to be "following" the aircraft at times. This effect is probably similar to "will-o'-the-wisp" or swamp ghosts, caused by the oxidation of methane in the presence of phosphine and diphosphane (swamp gases.) You have a chemical oxidation reaction that is "burning" but not enough to produce the bright visible light of a regular flame. The redox rate is not fast enough to be a human-eye-visible-burning but still can be seen when the redox rate is at the threshold, from time to time. The human eye can't see infrared light which is where most of the energy is going, with a random amount being hot enough to be visible, from time to time. The "foo fighters" are probably some similar effect of the exhaust. Looking sideways at an exhaust trail where this is happening, probably nothing can be seen. However, looking "end on" to an exhaust trail (i.e. your own or some other nearby aircraft's), you would be looking through possibly hundreds of feet of this exhaust plume and, when conditions are right, see a glowing ball and the accumulated light up and down the length from near-visible-flame reactions. Sightings would appear randomly, according to reports, and they somtimes seemed to "follow" the aircraft from which they were sighted and sometimes not. This fits my theory. Foo-fighters weren't seen during the day, of course, but at night this exhaust gas might have enough glow when looking through it "end-on" to be seen. Over Europe and over some parts of the Pacific, there would often be a parade of aircraft flying at night. An occasional sighting would not be surprising. Just my theory.
Wrestling is FAKE, though. Well, it's scripted, at least.