We had an Airbus 300 have an engine fire after takeoff at San Juan and the fire burned through the fire detector loop making the engine fire light go out so they landed with an engine on fire. A mechanic in back told the FA the engine was on fire but they landed with it running causing a lot of grief to the FO causing major problems with him. I know the captain who was on that flight. They dealt with what they saw on their panel, not looking out a passenger window. Let him rest in peace.