Even the dust particles settled on the surface of the aircraft or the ice crystals formed over the wing. All constitutes the mass of the aircraft. So till the fly is the part of the aircraft, (whether it be flying, sitting, dancing, falling, whatever), it constitutes in the weight of the aircraft. read more
The fly’s overall contribution to / effect upon the plane is no different than the fly’s contribution within any sized, sealed box of sufficient size for the fly to actually fly. Does it add weight — is the core, root question: No. The weight of the fly within the plane remains the same regardless of whether it’s in the air or at rest. read more