Passengers using United Airlines' "Easy Check-In" found it anything but that on Leap Day when the automated system failed, resulting in longer lines at its U.S. airport counters.
The Chicago-based carrier blamed the service interruption on software issues related to the leap year.
Spokeswoman Megan McCarthy says customers couldn't get Easy Check-In kiosks to confirm they had been checked in or print out their boarding passes for several hours.
McCarthy says no flights were delayed because of the problem. The airline apologized to customers for any inconvenience.
McCarthy says United didn't have any such problems with the software on Leap Day four years ago.