Unknown to be of hardware or software, or people error origin, via a quoted Katie Connel.
Delta Air had a computer problem, on Saturday. Cancellation of 40 or so flights, came about. Also an unknown number of flight delays were caused. Source
"Beware the Jabberwock, my son!
The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
The frumious Bandersnatch!"