Answer: tendency for external threat to increase affiliation
Explanation: The tendency for external threat to increase affiliation is a phenomenon which may be observed among individuals in a gathering or group whereby each individual often maintain a reserved status of keeping to one's self, however, when the gathering is exposed to threatening incident or scenes, dialogue persist between indivuduals in the gathering, which is at first relevant to the context of the external incident suffered by the gathering but may later transcend into different subject matter. The dialogue or discussion between passengers on the plane discussed above was due to the turbulence experienced by the aircraft.