Obvious examples that may not require the attendance of a medical professional to pronounce death would be a decapitated or badly decomposed body, multiple body disruptive trauma, where a body is severely burnt or has been subjected to prolonged submersion or has been predated by animals (where the body is missing essential parts).
Might vary by location, UK guidelines:
Not sure there are many opportunities for these cases in a flight, but you never know…
I sat next to a cougar on my last flight, and she destroyed my heart.
I think minced by the engine counts