"Preferred Overnight Airport close to the Academy"? Not sure I understand the question.
There are basically 2 airports. One in Colorado Springs, and one in Denver. Denver is about an hour from the Academy. There are more flights in/out of Denver. So; the cost to your nearest airport COULD be cheaper if you fly into Denver. A rental car is pretty much a given no matter which airport you fly into, if you're staying for a couple days. (Unless your cadet is a C2C/C1C - Junior/Senior). Then they probably have their own cars. The Colorado Springs airport can be just as inexpensive, if you live in an area that has an airport that flies into colorado springs. It all depends on where you're flying in from. But I'm not sure what you mean by an "OVERNIGHT Airport". You mean like "Red-Eye" flights?