Rashaad Penny's third touchdown turned the tide in No. 22 San Diego State's favor for good, and the Aztecs survived a back-and-forth challenge from Air Force 28-24 in the Mountain West Conference opener for both teams Saturday at Air Force Academy, Colo.

The lead changed four times from the late third quarter until Penny's 53-yard scoring rush put San Diego State (4-0, 1-0 MWC) ahead for good in a game that included a 90-minute lightning delay. Air Force (1-2, 0-1) had two opportunities to respond, but Arion Worthman's last-ditch pass attempt was intercepted by San Diego State safety Trey Lomax.

"A couple of the long runs, they blocked superbly," Air Force head coach Troy Calhoun said, adding praise for Penny's play. "Certainly, it helps having a big-play running back. He's one of those guys who can outrun a contain (defense)."

Penny's 53-yard score came after Air Force took its second lead of the fourth quarter. Running back Tim McVey hurdled a trio of San Diego State defenders en route to a 12-yard touchdown.

Tight end David Wells, who caught the game-winning score a week earlier against Stanford, took a 28-yard pass over the top from quarterback Christian Chapman for a touchdown. The score came in response to Air Force's first points after the second-quarter lightning delay.

Garrett Kauppila blocked a San Diego State punt that Lesley Dagler recovered at the San Diego State 4-yard line. Worthman punched in the touchdown two plays later, then found Marcus Bennett for a two-point conversion pass.

"We were just prepared that we're going to have go down and score on every drive," Air Force fullback Parker Wilson said. "Unfortunately, things didn't go our way in the end. (But) as far as the mentality, everyone was locked in and ready to go."

The first of the lead changes came on Penny's second touchdown, an untouched 20-yard run late in the third quarter.

Penny saved the drive with a spectacular, one-handed reception of a pass that came out of Chapman's hand awkwardly after a blind-side hit.

Penny's 128 yards were a season low for the nation's rushing leader, who came in averaging 196, but his three rushing touchdowns set a career high.

"San Diego State played quite, quite well, especially in the second half," Calhoun said. "Quite frankly, I wouldn't be surprised if they win at least 10 (game) and a couple beyond that, as well."

The 90-minute lightning delay midway through the second quarter provided San Diego State a spark, but Air Force made a defensive stop to maintain a 9-7 lead at halftime.

"I thought we were beat at the line of scrimmage on both offense and defense in the first two-thirds of the first half," San Diego State head coach Rocky Long said. "I thought we played better at the line of scrimmage (after the delay)."

The Aztecs' first play out of the locker room following the delay was a 42-yard pass from Chapman to tight end Kahale Warring, setting up Penny for a 2-yard touchdown run.

An Air Force pass interference penalty in the end zone on third down helped continue the San Diego State scoring drive. It was the second costly Falcons penalty of the possession.

Just before the delay, defensive lineman Santo Coppola leveled San Diego State punter Brandon Heicklen for a 15-yard roughing penalty to extend the Aztecs' first scoring drive.

Both offenses struggled in the first half, combining for just 213 yards of total offense amid driving rain. Wind gusts reached 22 mph, rendering passing difficult, while soggy field conditions limited rushing attacks that came in ranked No. 6 and No. 24 in the nation. Penny finished the half with 29 on 10 carries.

Air Force got on the board first with a 29-yard Ronald Cleveland touchdown run, the longest single play of the half for the Falcons' triple-option offense.

A botched snap denied Air Force points on the ensuing point-after attempt. Another special teams snap miscue almost cost the Falcons again just before the half, setting up San Diego State deep in Air Force territory, but John Baron's 39-yard field-goal attempt went wide left.

Air Force built a 9-0 lead before the lightning delay when kicker Luke Strebel made a 45-yard field goal.

NOTES: San Diego State is 4-0 to open a season for the first time since 1981. ... Rashaad Penny has scored at least one touchdown in every game on the 2017 season, and has reached the end zone in five-of-six dating back to 2016. ... Air Force's 52 penalty yards were the Falcons' most this season. ... The lightning delay was only the second in the history of Falcon Stadium. The other was in a game between Air Force and San Diego State in 1993. ... The win was San Diego State's first as a Top 25 team since 1977. The Aztecs lost their very next game after entering the AP Top 25 Poll twice in the 2016 regular season.