(REUTERS) - Some lucky customers who acquired United Airlines tickets at zero cost because of a computer programming error will be allowed to use them, an airline spokeswoman said on Friday.

"United has reviewed the error that occurred yesterday and decided that, based on these specific circumstances, we will honour the tickets," spokesman Mary Clark said in an email.

United did not say how many such tickets were issued on Thursday. The airline temporarily shut down its website to correct the error and also stopped booking flights through its phone center for about two hours.

Miscellaneous airport fees, such as the Sept 11 security fee, may have resulted in some passengers paying a nominal price for the tickets.