https://arstechnica.com/information-technology/2019/04/flight-data-system-outage-causes-april-1-airline-delays-no-fooling/

A fault in software used by most US airlines caused a wave of flight delays this morning across the US, affecting hundreds of flights. "Several airlines are experiencing issues with a non-FAA flight planning weight and balance program called AeroData," a Federal Aviation Administration spokesperson said in an e-mailed statement. "Mainline operations and regional operations are affected to varying degrees."

That software, provided as a service by AeroData Inc., is used to perform weight and balance calculations needed for flight planning—which is particularly important for airlines operating regional and commuter flights. Today's software outage only lasted for about 40 minutes, but it had a rippling effect across the US.