What was found
ENROUTE, ON TAKEOFF, FUEL SEEN VENTING FROM RIGHT WING TIP. LEFT TANK FUEL INDICATED 200 LBS LESS THAN RIGHT WING. BY THE END OF THE FLIGHT, UPON LANDING, LEFT TANK FUEL WAS 480 LBS LESS THAN RIGHT WING. MAINTENANCE REPLACED RIGHT WING TANK AIR RELEASE VALVE (FIM 87QM). OPERATIONALLY CHECKED OK.