Dear Trip Advisor - I rely on your service and have submitted several reviews. However while I am considering a trip to Mt Rushmore near Keystone SD when I searched for flights from your site you made the search for Billings, MT. I did more research and found Billings is a 6 hour drive to Keystone. The flight to Billings came through Denver, which is also a six hour drive to Keystone. Took a lot more research but I have found commercial flights to Rapid City, SD which is less than one hour to Keystone. I'm shocked at the choice you offered, unless I'm missing something. Please review this situation to make sure your choice is reasonable.