Nigeria Airways already flies from JFK to Lagos 2x per week. The flight is around 8 hours, so Miami would appear to be shorter. I don't know if it is only 6 hours though.
727, L1011, MD80, A300, 777-200, 737-300, 737-700, 747-400, 757-200, 737-800, A320. E190, E135, 767-200, CRJ9