A fire alarm triggered the evacuation of an air traffic control center in Elgin -- diverting airplanes and slowing some flights at the U.S.'s second busiest airport Monday morning.
The Federal Aviation Administration confirmed 79 arrival and departure delays at O'Hare and Midway International Airport occurred because of the mix up. Service was back to normal by 10 a.m. Monday, the FAA said.
"A fire alarm went off at FAA's Chicago TRACON after detecting water flowing into the pipes that would handle the sprinkler system," spokeswoman Elizabeth Isham Cory said. The Terminal Radar Approach Control facility in Elgin handles flights 40 miles out of O'Hare.
No water came down but air traffic controllers were evacuated until 8:30 a.m. and employees at the FAA's long-distance control facility Chicago Center in Aurora took over airspace operations.
The FAA is investigating what caused the alarm.
There were 20 arrivals delays of between 15 and 30 minutes at O'Hare and three at Midway. A significant number of flights were late departing -- 53 at O'Hare and three at Midway.
Seven flights headed to O'Hare and one destined for Midway were diverted.