Oops! United Airlines Accidentally Offers Airline Tickets for 'Free'

The next time you're sitting on a full-price seat on a United Airlines flight, the person next to you, likely hogging your armrest too, may have paid just $5, or less.

An unknown number of United Airlines customers purchased flight tickets for practically nothing Thursday after a computer glitch caused some fares to show up online for anywhere from $10 to $0.

"I just booked a couple of round trips from SJC - BOS via IAH in November and December for $10 round trip. Found them on United.com," user Quiltingatty posted on FlyerTalk.com, an air travel online forum.

"UA: IAD - MSP $5 each way Sept 25th/26 th… Just went to book this for a work trip and ended up paying $7.50 all in," posted another user on the same site.

"During this time I'm looking up everything," said Dawnica Jackson, a United Airlines customer who rushed to book flights after seeing the glitch. "I'm like, we're going here. We're going there. I was like we're going to do Christmas in Maui."

As word spread online of the deals, United quickly shut down the booking section of its website and phone centers to prevent more tickets from being sold.

The website began again accepting reservations, at the normal prices, around 2:45 p.m., CST.

A spokeswoman for the Chicago-based company told the Associated Press the error was not a website malfunction but an error in filing the fares. The airline does not know how many of the bargain-priced tickets were sold, nor does it know how it will handle the tickets that were sold.

"As always, we will do what is appropriate," United spokeswoman Megan McCarthy said.

United did not reply to ABC News' request for comment as of this writing.