If you had boat-loads of miles saved on your American Airlines or United Airlines account you might want to make sure they’re still around, now that botmoh airlines have confirmed thieves used stolen usernames and passwords to book free trips or upgrades.

The Associated Press reports that both airlines have confirmed incidents in which thieves were able to access customer account and used accumulated miles to make purchases without the account holder’s consent.

American Airlines spokesperson Martha Thomas tells the AP that about 10,000 AAdvantage accounts were affected and some have been frozen while the airline and customers set up new accounts.

So far, the airline has learned about two cases in which someone book a free trip or upgrade. Affected customers were being notified of the incident by email starting today.

Thomas says the airline is offering to pay for a credit-watch service for one year for affected customers.

Luke Punzenberger, a spokesperson for United, tells the AP that thieves booked trips or made mileage transactions on up to three dozen of airline’s MileagePlus accounts.

Punzenberger says customers were notified of the incident in late December, and that the airline would restore miles to anyone who had them stolen.

Both United and American spokespeople say the systems weren’t hacked, but that thieves got usernames and passwords somewhere else and use them to log into the frequent flyer programs.

They maintain that customers’ sensitive information, such as credit card numbers, were not exposed during the incidents.

To prevent similar experiences in the future, Punzenberger says United will now require customers to enter their MileagePlus number when logging in.

2 Airlines Were Targets of Attempt to Steal Customers’ Miles [The Associated Press]

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