According to John J. Townsend, Managing Deputy Commissioner in charge of Safety and Security for Chicago's Airports:

The City's entire airport system is currently at a security level four, reflecting the highest measures of security. Increased security measures are directed by the Federal Aviation Administration. Additional measures have been implemented by the City Department of Aviation, the Chicago Police department, Multi-Agency Federal Law Enforcement Agencies, the Airlines and other airport tenants.

These measures include: increased patrol by uniformed law enforcement, specialized canine detection units, and undercover units throughout the entire airport facility as well as roadways, public transportation and parking facilities.

All passengers and crew of general aviation flights will be subjected to the same security screening process as passengers and crew on commercial flights.

Collectively these efforts are comprehensive and will continue to provide the traveling public and Chicago's Airport community with the highest levels of Security.