The numbers were loaded erroneously May 16 because of an oversight and were removed on Wednesday, United Continental said. Neither number will be used again, according to the airline, which was rebuked by unions representing pilots and flight attendants over the reuse of the numbers.

Numbers 93 and 175 were assigned to Continental-operated flights that were also going to carry United’s booking code, according to Airlineroute.net, which tracks schedule data. United and Continental merged in October and will operate separately until regulators grant them a single certificate.

United Flight 93, a Boeing 757, crashed in a field near Shanksville, Pa., as passengers tried to take the cockpit from hijackers. Flight 175, a Boeing 767 en route to Los Angeles from Boston, was flown into the World Trade Center.

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