Complex sentence: Rimmer initially concludes that the spacecraft encountered is alien and they are attempting to contact the Red Dwarf crew in order to return Glenn Miller, whose plane went missing in 1944 and was never found.
Split into simpler sentences: Rimmer initially concludes that the spacecraft encountered is alien and they are attempting to contact the Red Dwarf crew in order to return Glenn Miller. This references the alien abduction myth of Miller, whose plane went missing in 1944 and was never found.