Johnson knocked down four 3-pointers to lead the Bulldogs and Marvelle Harris added 12 points.
Fresno State (10-13, 3-7 Mountain West) capitalized on Air Force's 4 minute and 19 second shooting drought late in the first half to take off on an 8-0 run and lead 29-19 at the break.
The Falcons (9-12, 3-7) climbed within six after Hayden Graham made a 3-pointer, but the Bulldogs quickly responded with a 10-0 run to shoot ahead by 14 points with 5:04 left to play.
Marek Olesinski scored four 3-pointers on 6-of-13 shooting to lead Air Force and finished with 17 points. The Falcons went the final 2 minutes without a basket as Fresno State closed out the game with nine uncontested points.