The Mirrorball Man wrote:
It could be carried by an African swallow!
Don't start that!
Honestly, some things just don't seem right in the movies. For instance, the area where Spock's casket landed is curiously landlocked, suggesting that the Enterprise crew wanted his casket to land there. (depending on what theory you go with)
Any kind of release system, would be like installing an emergency burial bell - in case the occupant isn't actually dead. Although Spock's case is unique, in that his katra wasn't dead, his body had ceased to be and was nothing more than an irradiated corpse that would require isolation.