Tens of thousands of air passengers were stranded Tuesday as aviation giants Lufthansa and Air France were hit by strikes that crippled traffic at several major European airports. Germany's biggest carrier Lufthansa was forced to cancel 800 out of 1,600 scheduled flights, including 58 long-haul flights, as German public sector workers including ground crew and airport firefighters walked out between 5:00 am and 6:00 pm (0300 and 1600 GMT). Tuesday's "warning strike" hit Germany's biggest airport Frankfurt as well as other regional hubs such as Munich, Cologne and Bremen.