According to the Washington Post, Biden's plane was landing as one of the two smaller planes was taking off and another was coming in for a landing. Twenty-nine people were onboard the SkyWest Airlines Canadair jet from Muskegon, Michigan, which was landing. The plane taking off was an ExpressJet Airlines Embraer ERJ-145 to Buffalo.
Biden's plane was not involved in the close call and he was never in any danger-- but his arrival led to confusion as to how air traffic on one runway was being handled. The NTSB is investigating.
Biden was in town for the inauguration of Chicago Mayor Rahm Emanuel. A helicopter was nearby to follow his motorcade and that pilot was reportedly talking to the air traffic controller in question, the Washington Post, reports.