An officer shot and killed a dog who attacked him on the city's West Side, and two other officers were also injured in the incident on Monday afternoon, Chicago police said.
Hundreds of flights have been canceled and thousands are delayed, with Newark Liberty International Airport and Philadelphia International Airport hit the hardest.
Ald. Timmy Knudsen said the Chicago Police Department is increasing patrols in the area, conducting targeted robbery enforcement and reviewing surveillance video as investigators work to identify the suspects.