I'm wondering when exactly did AA and UA consolidate their control over the O'Hare market. It seems right after deregulation into the early 80s, according to several timetables I have Delta, Eastern, Northwest and TWA all had a larger than average presence at O'Hare. By the mid 80s, all 4 airlines had pulled back from O'Hare. Delta and Eastern had no connecting possibilities at O'Hare but lots of point to point service to cities in Florida and the Southeast (In Eastern's case to the Carribean also) that would later be flown by AA and UA exclusively. Any idea when these carriers pulled back from O'Hare and when they sold their slots (if O'Hare was in fact slot controlled in the 80s)?