Complex sentence: Since that time there have been no scheduled passenger flights out of the Gary/Chicago Airport, but charter airlines frequently fly casino trips to Atlantic City, Harrah's Tunica, and Beau Rivage Biloxi.
Split into simpler sentences: Since that time there have been no regularly scheduled passenger flights out of the Gary/Chicago Airport. However, charter flights are frequently scheduled for casino trips to Atlantic City, Harrah's Tunica, and Beau Rivage Biloxi.