Each month there are several airlines that offer direct flights from Denver (DEN) to Chicago (ORD). Among the top airlines that consistently provide DEN to ORD flights include: American Airlines - (AA) with 270 direct flights between Denver and Chicago monthly United Airlines - (UA) with 810 direct flights between DEN and ORD monthly Frontier Airlines - (F9) with 30 direct flights between Denver and Chicago monthly Southwest Airlines - (WN) with 240 direct flights between DEN and ORD monthly Delta Air Lines - (DL) with 150 direct flights between Denver and Chicago monthly