A computer problem with the FAA automated flight planning system in Atlanta caused major delays at Hartsfield-Jackson Atlanta International Airport, the world's busiest, this morning as well as other airports up and down the East Coast of the US. The computer problem started at about 0500 EST and ended at about 1000 EST. Delays are expected to continue through the rest of today, which were already climbing because of bad weather in the US.
This article from July in eWeek says that the FAA was transitioning then to a new flight planning system that was supposed to end these types of outages and implied that the transition was almost complete. It is unclear, however, whether this latest problem was in this new system or not.