I agree that an unincorporated group owning an aircraft will not ordinarily be a partnership, because the group members are not engaged in a joint venture with a view to profit (this assumes that the aircraft is only used privately and is not rented out or used for paid instructional work).
That is an interesting point you raise there and would certainly indicate that if you want to do either of those activities with your asset one would have to cover the liability aspect probably in a more formal way than 'a group'
FD