Secrets of Fliegerhorst Kaserne lay underground (Langendiebach) near Hanau

I posted this several years ago on this website, but didn't get much of a response. I have been looking for info on Fliegerhorst Kaserne (Fliegerhorst Langendiebach- an old Luftwaffe airfield near Hanau, Germany now used by the US Army). There are apparently some underground bunkers there under the airfield which, now filled with water, at one time housed aircraft I spoke with a gentleman who had actually been in a sealed room near the old steam plant (accessed from there) & said there were rusty helmets, etc. in there & that CMD threatened them with UCMJ for trespassers. Tunnel entrances in wall of steam plant basement were later bricked over. My BN CDR also said there was a bricked-over entrance to a tunnel in the basement of his quarters on Fliegerhorst. There is a printed local history in the U.S. forces library in Hanau, which states that in1979, a 2-1/2 ton truck fell through the street and uncovered a network of tunnels, equipment for pumping water on and off the airfield for concealment, and 3 underground bunkers on the airfield which contained aircraft parts and a lot of water. I used to be stationed there in the late 90s & found some "Suspicious areas", but nothing definitive. Can anyone provide info on this? soldier20@hotmail.com

Although I have been in off-site contact with the OP, to complete the record here, I was stationed on this base from early 2024 until it effectively closed in late 2024. (Today it is back under German control, and as of this writing, it has not yet been repurposed, though there are pending plans to relocate a small local Luftwaffe museum located in nearby Hailer to the former control tower.).

While there are a number of interesting stories pertaining to Fliegerhorst Langendiebach (just as there are with virtually every other former Luftwaffe site), there is nothing definitive to report. Yes, there are definitely underground facilities on the field, most prominently located under the largest of the remaining hangars (the former 127th Aviation Support Battalion hangar). These are bricked-off; however, the best-available historical evidence suggests that they were designed for parts storage, rather than aircraft hangaring. The prevailing rumor is that Allied Forces believed -- or saw conclusive evidence -- that some of these these areas had been booby trapped (or contained unexploded ordnance), and seeing nothing of significant value, they simply chose to permanently seal them off. There has long been interest on the part of American soldiers on the field in breaching these entrances, but none were ever able to obtain sufficient official backing to undertake the effort.

It seems likely that some artifacts remain, though after decades of water submersion, it is doubtful that any would be in salvageable condition. Further, as there were other airfields in the immediate vicinity (Rothenbergen, Gelnhausen) known for hosting combat units, the relative interest level in Langendiebach's training units has typically been somewhat lower -- notwithstanding the "secret" bunkers and such. To the east, Rothenbergen's bunker complex is better known, as it was extremely large (1,000 person capacity), and at least one entrance (now sealed for safety reasons) is still visible from the main road leading into town just off of Autobahn 66. In fact, most of the houses built on the high ground on the west side of town (Hühnerberg) now sit directly atop this complex.