Ikarus, the Flying Man.

Two French spies, Baron d’Aubigny and Clemence de Montignon, blackmail German engineer Günther Ellinghaus with his gambling debts into handing over his construction plans for the new Ikarus engine. He flees to New York and works as a waiter. When World War I breaks, he signs on as a fireman on a Dutch ship and returns to Europe. He becomes a fighter pilot in Germany and faces the former spies as his enemies. After an emergency landing he is taken into their headquarters. He escapes an attempted murder and fights his enemies in an air battle. Both of them survive and after the war Ellinghaus offers them his hand in reconciliation.