For a little while on Thursday, United Airlines was giving away airplane tickets for free, or close to it.

Passengers reported buying tickets for $5 to $10. United says it accidentally filed fares for $0, although airport charges might have resulted in a small cost.

United stopped taking bookings through its website and phone centers to prevent more of the tickets from being sold or given away. The website was accepting reservations again around 2:45 p.m. Central time.

United spokeswoman Megan McCarthy says the mistake was due to an error in filing the fares, not a problem with the website. The airline doesn't yet know how many tickets were sold at the unusually low prices.

She says United has not yet decided whether it will honor the tickets.