Colorado faces Air Force at Falcon Stadium for the first time since 1974.
The Buffaloes are in danger of starting 0-2 for the first time since 2012. They lost 38-13 to TCU in the opener.
The Falcons received votes in the Associated Press Top 25 after a win over Northern Iowa.
Air Force has a 20-33-2 all-time mark against the Pac-12.