Well, to determine if JL 50 is a real story, we need to look at its source, the details presented, and any available background information. But as of now, with just the name, it's impossible to tell.
One popular Langley AFB ghost story is about a phantom pilot. People claim to have seen the figure of a pilot in an old flight suit near the old hangars at night. It's said he was a pilot who died in a tragic accident long ago and his spirit still lingers.
The 'jl 50' real story remains a mystery without further details. It could potentially be a story in a specific community or field. For example, in a small town, 'jl' could be a family name and '50' might be related to a family anniversary or a particular event that happened 50 years ago within the family. It could also be related to a business where 'jl' is the initials of the company and '50' is a significant number for the company's history, like the 50th product launched or 50th employee hired.
A unique feature is the clash of two very different universes. Naruto's world of ninjas and chakra is completely different from Asuka's mecha - piloting world in Evangelion. This contrast makes for really interesting storylines.
I'm not sure specifically which 'jl 50 plane' you are referring to. There could be many planes with various designations. It might be a very specific model within a certain region or a project that is not widely known. Maybe it's a military - related plane or an experimental one.