United Airlines briefly gave away tickets for free or negligible fees on Thursday.
The company accidentally filed fares for zero dollars, although airport charges could have resulted in a small cost. Passengers reported buying tickets for $5 to $10.
Passengers say they are waiting to see if United will honor the tickets.
The airline stopped taking bookings through its website and phone centers for a short time to prevent more sales, but resumed operations at 2:45 p.m. CST.