Rackstraw may have been the skyjacker, but the decoder doesn't offer enough info about his method for us to know what he means by "a system of letters and numbers", so at this point it seems like a suspect-based "proof."
--------------- Von Konigswald: Jack the Ripper plays shuffleboard. -- Happy Birthday, Wanda June by Kurt Vonnegut, c.1970.
Maybe they will publish what this decipherment was like. Maybe it really does not prove anything.
Interesting thing to me about this case (like that of the three convicts who fled Alcatraz in 1962 but were never found (it may be, oddly enough, one of them recently wrote to the FBI from South America that they did escape to the mainland)). I keep hoping it isn't solved - part of me enjoying the physical testing these people (the convicts, "Cooper") put into their schemes - sort of like wishing they succeeded.
But these are the same people who interviewed the pilot and the stewardess who spent the most time with the hijacker and both of them when shown a photo of Rackstraw adamantly said he was not the hijacker. I think they have a fixation on Rackstraw and are just pulling things out of their butt at this point.
These are not clues, Fred.
It is not yarn leading us to the dark heart of this place.
They are half-glimpsed imaginings, tangle of shadows.
And you and I floundering at them in the ever vainer hope that we might corral then into meaning when we will not.
We will not.