I remember an old movie where some government or research facility will be concerned about a lot of missing planes and ships. They don’t disappear in the Bermuda triangle (I think) but simply disappear. They determine that all the ships and planes disappear into an alternate dimension and they are even able to view that dimension: It’s in black & white, with silhouettes of the disappeared ships & planes sliding past them on either side.

I don’t remember how that movie ends, but I saw it about 25 years ago. It was in English, but I think it was in color. Sorry I can’t give any more details. 🙁