ORD had a 21 minute power failure around 3:50 p.m. today. It hit T 2, 3, and 5. The TSA had to reboot their systems, causing long delays. AA was affected the most, UA not very much (They're in T1). They're trying to figure out what caused it. What, TSA and other aspects of the facility don't have backup power supplies? If anyone was there, please post your personal observations of the mess.