Airfare mistakes don’t come around every day, but when they do, it can mean cheap flights for travelers. In fact, sometimes it can mean crazy cheap flights for travelers. Yesterday was one of those days. Two very distinct airfare mistakes occurred, and we at FareCompare caught them.

Lufthansa had a fuel surcharge misfiling, and released a series of U.S. to Europe airfares without fuel surcharges. These airfares were gone quickly, but while they lasted, travelers could find incredible savings. People were able to grab flights to Europe for hundreds of dollars less than they would pay if they had searched just a few hours later. Just as an example, there were Chicago to Frankfurt flights for under $400 r/t (taxes and fees incl.).

The other airfare mistake belonged to American Airlines. The carrier released their Weekender Fares as they are wont to do. Weekender Fares are usually only good for the two weekends (travel Friday – Monday or Tuesday) following the filing. However, this time they were missing the travel date restriction, so you could actually find weekend travel deals throughout the summer, which made many of those airfares a real bargain.

In order to jump on these and other airfare mistakes, you have to know about them. At FareCompare, we provide real-time airfare alerts from your home airport via Twitter, as well as free airfare email alerts. These tools give you a chance to see when prices have dropped and when great deals are available, whether an airfare mistake has occurred or not.