AIR FORCE ACADEMY, Colo. (AP) -- A failed play at the end of the first half made all the difference for Brigham Young. John Beck hit Todd Watkins on a 70-yard touchdown pass on the second play of the third quarter and threw three more touchdown passes in the half, helping BYU overcome a sluggish start and beat Air Force 41-24 on Saturday. "What I thought was the turning point was the third-and-long just before the half," BYU coach Gary Crowton said. "We did not get it, but there was a play where we had Todd Watkins open. I saw that play and we kind of changed our plan a little bit based on how they were playing defense. To me, that was the play." BYU (4-4, 3-1 Mountain West) struggled through most of the first half, managing a field goal on its first possession and not much else. After seeing Watkins blow through Air Force's defense at the end of the second quarter, Crowton tweaked his offense to include more plays deep and down the middle. It worked. BYU had three touchdowns and a 222-49 advantage in total yards in the third quarter, turning a seven-point deficit into a 24-10 lead. BYU kept it going in the fourth quarter, scoring 38 points in the half and finishing with 527 yards. Dennis Pitta blocked a punt and caught two touchdown passes, Watkins had six catches for 153 yards, and Curtis Brown ran for 128 yards in the Cougars' third win in four games. "I felt like we came out flat in the first half," Pitta said. "We came out sluggish, but we turned it around in the second half." Air Force (3-4, 2-2) seemed out of sorts coming off its bye week. The Falcons couldn't get much going with their option -- 213 yards on 47 carries -- didn't give quarterback Shaun Carney much time to throw and allowed a touchdown off a blocked punt for the third time in two games. Air Force also was uncharacteristically undisciplined, finishing with nine penalties for 70 yards and numerous miscues on pitches and passes. The Falcons did score twice in the fourth quarter, including Darnell Stephens' second TD run, but couldn't get closer than 10 points. "We're still looking for that complete game," Air Force coach Fisher DeBerry said. "We've played seven games now and we have not had a game yet where I feel we've played a complete game yet of four quarters of our best football." Beck had something to do with it this time. The sophomore shook off a difficult first half, hitting Watkins on a 70-yarder 33 seconds into the third quarter. Beck followed with a 38-yard pass to fullback Naufahu Tahi on the next drive, setting up an 11-yard touchdown pass to Pitta on a screen. Beck also tossed a 14-yard touchdown pass to Austin Collie on the first play of the fourth quarter to put BYU up 31-10. He finished 20-for-31 for 319 yards. "I wish I could have come out a little better at the start," Beck said. "Sometimes I come out a little bit antsy, but then I settled down and I felt like I was in my groove." Air Force followed Collie's touchdown with a 26-yard touchdown pass from Carney to Greg Kirkwood just 34 seconds later, but that only cut the lead to 31-17 because of yet another miscue by punter Donny Heaton. Heaton had two punts blocked and four others that went less than 20 yards last week against New Mexico. He didn't have any trouble with four kicks in the first half, but dropped a snap late in the third quarter. Pitta moved in for the block -- BYU's first in 12 years -- and Gary Lovely ran it in eight yards for a touchdown that put the Cougars up 24-10. "We had some breakdowns in the kicking game that concern me a great deal," DeBerry said. It was a surprising turnaround after the way BYU started. Beck seemed off-kilter in the early going, repeatedly sailing passes over and behind his receivers. He overthrew Collie on what would have been a touchdown on BYU's second drive and his first pass of the second quarter was thrown behind Daniel Coats, leading to Bobby Giannini's interception at the Cougars 29. Air Force, after managing just 50 yards on 18 plays in the first quarter, capitalized on the next play when Stephens took off left and cut back across the field for a 29-yard touchdown run. The Cougars had another mistake three plays later, when Brown fumbled a handoff from Beck and Air Force's Nate Terrazone recovered at the BYU 36. That set up Michael Greenaway's 48-yard field goal that put the Falcons up 10-3. "I felt like we were playing too nervous, too tight (in the first half)," Crowton said. "The plays were there, the opportunities were there, but little things hurt us. I think with confidence those things will go away and I think our team gained a little confidence."