We do not have enough data on this route to provide a reliable graph showing how many days before departure it is the best to book.
However, usually the closer it is to the departure, the more expensive the tickets are.
Direct flights last about 2h 49min.
Direct flights available 3 days a week - Monday, Friday, Saturday.
Direct flights: United Airlines (UA), American Airlines (AA).
Chicago (IL) San Antonio (TX)