The Federal Aviation Administration has not done enough to improve how air traffic controllers handle emergency situations, an independent watchdog reported Friday.

An inspector general’s report on the FAA’s response to major air traffic control disruptions showed the agency tried to improve its processes in the wake of a major fire in Chicago in 2014 that cost $350 million to “aviation stakeholders and airlines.” The 2014 fire at the Chicago Air Route Traffic Control Center destroyed critical FAA communications infrastructure and caused thousands of flights to be canceled or rerouted because air traffic controllers couldn’t communicate with planes, causing problems at Chicago O’Hare International Airport and Chicago Midway Airport.