The shepherd by Frederick Forsyth

Christmas Eve, 1957. For one Royal Air Force pilot, one last hurdle remains between himself and a cozy Christmas morning in England. A sixty-six-minute flight in his Vampire fighter plane from Germany to Lakenheath. A routine flight plan and a full tank of fuel. What could go wrong? But as the fog begins to close in, the compass goes haywire and the radio dies, leaving him in silence, lost and alone up in the inky black sky. All hope seems lost as he accepts his fate when, out of nowhere, a vintage fighter-bomber appears and is miraculously trying to make contact. For one lonely pilot this is a miracle, but really the mystery has just begun.