A fire set by an alleged rogue contractor raised questions about why the Federal Aviation Administration had to ground flights in and out of Chicago for hours Friday, and what kind of vetting and security procedures the workman who allegedly set the fire had to face.

http://www.suntimes.com/30127361-761/experts-grounding-shows-fragility-of-air-traffic-system.html#.VCcFwxbCecx