AIR FORCE ACADEMY, Colo. (AP) — Ryan Harrison’s 33-yard field goal on second down gave Air Force a 20-17 overtime victory over TCU on Thursday night, keeping the Falcons unbeaten under new coach Troy Calhoun.

The Falcons (3-0, 2-0 Mountain West), who overcame a 14-point fourth-quarter deficit, were swarmed on the field by thousands of cadets who hadn’t had this much to celebrate in a long, long time.

Harrison’s winner followed a miss by TCU kicker Chris Manfredini, whose 36-yard attempt hit the left upright on the first possession of overtime.

The senior has missed just six times in his career and two of them were on this night.

The Falcons had tied it on Jim Ollis’ 71-yard TD run on an option pitch from Shaun Carney with 5:55 left, the very kind of play that worked so well during most of Fisher DeBerry’s 23 years at the academy.

The Frogs (1-2, 0-1), still smarting from their 34-13 loss at Texas on Saturday, were lethargic and sloppy, failing time and again to capitalize on short fields and prime opportunities.

They were well within Manfredini’s range with the wind at his back going toward the south end zone in the final minute of regulation when they went for the touchdown instead on first-and-10 from the 22 only to see cornerback Carson Bird snare Andy Dalton’s underthrown pass to Jimmy Young in the end zone.

Twice in the third quarter, the Horned Frogs were turned away near the goal line, on a blocked field goal and an interception.

Finally, Dalton hit Walter Bryant in the back of the end zone for an 11-yard score one play after the Frogs got a first down by the nose of the football, to make it 17-3 with 13:10 left.

The Falcons had fared far worse on offense, so this looked like a lock for the Horned Frogs.

But Carney responded by hitting Travis Dekker for 50 yards, setting up a 9-yard touchdown strike to Keith Madsen that pulled the Falcons within a touchdown with 8 minutes remaining.