A flight information communication system has a plurality of RF direct sequence spread spectrum ground data links that link respective aircraft-resident subsystems, in each of which a copy of its flight performance data is stored, with airport-located subsystems. For this the four retractor valves are guided by sleds in radial guide slots of a base plate. The first sensor surface is exposed to allow sensing of a first variable. The free layer structure, positioned adjacent the antiparallel coupling layer, includes a first free layer having a magnetic moment and a second free layer having a magnetic moment pinned antiparallel to the magnetic moment of the first free layer.