What was found
PHL FLT 742 EN ROUTE PHL TO BCN. ABOUT ONE HOUR INTO THE FLIGHT, THE CREW TWICE NOTICED A STRONG ELECTRICAL BURNING ODOR, WHICH TWICE DISSIPATED SHORTLY AFTERWARDS. THE CREW NOTED THAT TURNING OFF THE FIRST OFFICER`S FOOT HEATER ELIMINATED THE ODOR ALTOGETHER. THE FLIGHT RETURNED TO FIELD PHL AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE PLACED THE AIRCRAFT ON MEL. (S)