Credit: Jason Rabinowitz/@airlineflyer https://twitter.com/AirlineFlyer/status/593231643143479297/photo/1

Several American Airline flights were delayed yesterday after an iPad app used by pilots crashed the device. The app acted as an electronic version of a “flight bag” of printed documentation.

AA got regulatory permission to use iPads in-flight in 2012 when it proposed using them to store digital versions of aircraft operating manuals and other documents. In AA’s case the printed versions ran into the thousands of pages and could weigh up to 35 pounds. The airline pegged this as saving more than a million dollar’s worth of fuel each year because of the lower weight.

The precise details and extent of this week’s problem haven’t been confirmed by AA, other than to say a “few dozen flights” were affected and that some planes had to return to the gate before a planned takeoff to fix the problem through a Wi-Fi connection.

Passengers on one flight told The Verge that the pilot had announced that both his and his co-pilot’s iPads had gone completely blank. A passenger on another flight reported that the pilot there had to completely reboot two systems. It also appears that the problem wasn’t limited to plane manuals, but that the glitch may have made specific flight plans inaccessible, though that isn’t confirmed by AA.