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 before United shut down the bookings on its website and phone centers to prevent more tickets from being sold or given away.
The airline said it accidentally filed some fares for $0. Airport charges might have resulted in a small cost seen by some passengers.
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The website was accepting reservations again around 2:45 p.m. Central time.
Such fare mistakes have happened before, often when an airline dropped a digit when entering fares into its computer system.
That may be what happened here. United Continental spokeswoman Megan McCarthy said the mistake was due to an error in filing the fares, not a problem with the website. She said United doesn't yet know how many tickets were sold at the unusually low prices.
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United says it will honor all tickets purchased.