Heard about this from a former GF in the airfreight business back in the early '70's, a light plane was bringing a loaded coffin and other small packages from Mt Isa to Brisbane, and had a fuel stop in the middle of the night in the middle of nowhere, at altitude about 20 mins later, the pilot, the only 'living' thing on board experienced a nudge on the shoulder, fearing the worst, he slowly turned, to see a black cat, it must have snuck on board during refuelling earlier. Much relief. !