United Airlines will honor the free tickets.
The problem Thursday was that the airline accidentally filed fares for zero dollars, although airport charges could have resulted in a small cost.
"Yay," said Nancy Ilk, a consultant who flies often from Blooming Prairie, Minn., who got one of the tickets."I'd love to find out how many tickets actually got booked for the really inexpensive fares."
She paid $10 to fly from Minneapolis to Houston and Washington's Reagan National and back in October. The $10 was noted as a Sept. 11 security fee.
The airline temporarily stopped taking bookings through its website and phone centers to prevent more sales. But the website resumed accepting reservations by mid-afternoon.
"United has reviewed the error that occurred yesterday and decided that, based on these specific circumstances, we will honor the tickets," said spokeswoman Megan McCarthy.
No word on how many tickets are at stake.