By Nicole Jao NEW YORK, Feb 22 (Reuters) - Electricity firm Entergy Corp hit fourth-quarter profit estimates on Thursday, as unplanned outages at its customers' facilities and slower-than-expected ramp ups curbed industrial sales. New Orleans, Louisiana-based Entergy operates power plants that supply electricity to about three million customers in Arkansas, Louisiana, Mississippi and Texas. "Industrial sales were strong but not as robust as anticipated going into the quarter due to outages at customers' facilities and slower ramp-ups from new and expansion customers," said Kimberly Fontan, CFO of Entergy. For the full year, Entergy's retail sales were flat compared with the prior year at 27,320 gigawatt hours (GWh). The energy company posted earnings of $111 million, or 52 cents per share, on an adjusted basis for the fourth quarter, hitting analysts' estimates, LSEG data showed.