The Broncos (2-1, 1-0 Mountain West Conference) pulled away in the second half while slowing a Falcons running game that had piled up 139 yards in the first half. Boise State outscored the Falcons 21-3 in the final two quarters and had two other scoring drives scuttled by turnovers.
Ajayi rushed for 125 yards on 17 carries, the sophomore's second game with more than 100 yards rushing. He scored on long runs of 35 and 20 yards after beating defenders around the corner and racing down the sideline.
Meanwhile, Southwick was sharp throughout the game, putting together the most accurate passing game in school history. He was 27 of 29 for 287 yards and spread the ball to six receivers. His favorite target was Matt Miller, who had 10 catches for 112 yards.
Boise State totaled 533 yards on offense and was 8 of 10 on third downs in beating the Falcons for the second straight time.
Air Force (1-2, 0-2) stayed close in the first half thanks to the rushing of quarterback Jaleel Awini. Making just his second career start, Awini led the Falcons with 107 yards on 23 carries in the game.
But the Falcons couldn't do much else on offense. Awini was 4 of 9 for 99 yards and his one interception in the fourth quarter squelched any chance of getting closer to Boise State, which led 35-20 at the time.
The Broncos have won two straight after a disappointing opening loss at Washington. They play at Fresno State next week.