In the early days of aviation, pilots had little chance to contemplate non-essential activities. Flying demanded constant attention, and the wind and engine noise in a slipstream-blasted open cockpit all but drowned out normal conversations. In the early years of instrument flying, the effort involved in "flying the beam" (navigating a course determined by the intersection of ground-based radio signals by straining to listen through a headset to a scratchy audio stream of "dits and dahs") also forced pilots to concentrate on flying duties during instrument meteorological conditions.[3]