9/11 flight numbers 93 and 175 were accidentally used for two Continental Airlines flights. United apologized but would not explain how the error happened.
United Airlines temporarily revived the flight numbers of two hijacked planes used in the Sept. 11 attacks but said Wednesday the move was inadvertent and they would not be used.
"We are taking immediate steps to remove them and apologize for the error," a United spokesman said.
Call numbers 93 and 175 were mistakenly assigned to two flights by Continental Airlines, which has merged with United.
United declined to explain how the numbers found their way back onto flights. Unionized flight attendants urged the company to permanently retire them, while pilots said the move was insensitive.