Each month there are several airlines that offer direct flights from San Francisco (SFO) to Chicago (ORD). Among the top airlines that consistently provide SFO to ORD flights include: Alaska Airlines - (AS) with 300 direct flights between San Francisco and Chicago monthly American Airlines - (AA) with 270 direct flights between SFO and ORD monthly United Airlines - (UA) with 480 direct flights between San Francisco and Chicago monthly Delta Air Lines - (DL) with 180 direct flights between SFO and ORD monthly Southwest Airlines - (WN) with 90 direct flights between San Francisco and Chicago monthly