ANNAPOLIS, Md. (AP) — Navy and Air Force have been playing each other in football since 1960, and this is the earliest the teams have ever met.

When the two service academies announced late last year that the game was being moved from its usual spot in early October, no explanation was needed.

Navy-Air Force on Saturday took center stage to some degree as the American sports world observed the 20th anniversary of the 9/11 attacks. Players from both teams carried flags onto the field before kickoff. There was a moment of silence before the national anthem, and then a flyover featuring two Lockheed Martin F-35B Lightnings and two Boeing F/A-18 Hornets.

Elsewhere, Army’s players also carried flags onto the field for their home game against Western Kentucky. At Nebraska, former Navy SEAL Damian Jackson, a 29-year-old backup linebacker, led the Cornhuskers onto the field carrying a flag and flanked by first responders, including a health care worker.

Nebraska coach Scott Frost presented the family of fallen Marine Cpl. Daegan Page with a Cornhuskers jersey before the game. Page was one of 13 U.S. service members killed Aug. 26 in a terrorist bombing at the Kabul airport in Afghanistan. The 23-year-old Page was from Omaha.

At Minnesota’s game against Miami of Ohio, the family of the late Tom Burnett Jr. was honored on the field after the first quarter. Burnett, a native of Minnesota, was one of the passengers on Flight 93, which crash-landed in rural Pennsylvania on 9/11.

In a ceremony before its game against Kennesaw State, Georgia Tech recognized Atlanta police officer and former New York City paramedic Jay Pagan, who worked at the Twin Towers on search and rescue following the attacks and was trapped in debris. Pagan was presented the game ball in a pregame Heroes Day ceremony.

Boston College wore its red bandana uniforms against Massachusetts, and names were replaced by “For Welles.” Since 2014, the Eagles have occasionally worn uniforms with red bandana trim in memory of Welles Crowther, a former BC lacrosse player who died helping to rescue people from the World Trade Center during the 2001 attack. Survivors identified Crowther by the red bandana that he was known for wearing at all times.

At the U.S. Open in New York, before the start of a women’s final between two players who weren’t even born yet on 9/11, female cadets from the U.S. Military Academy unfurled a giant American flag that covered almost the entire court at Arthur Ashe Stadium. While Britain’s Emma Raducanu, 18, and Canada’s Leylah Fernandez, 19, played, “9/11/01” was stenciled on the side of the court.

At Richmond Raceway in Virginia, a 1,100-pound piece of steel from the Twin Towers was on display on the midway, along with a Wall of Remembrance. Cub Scouts led the Pledge of Allegiance before the afternoon NASCAR Xfinity race kicked off a racing doubleheader.

Dale Earnhardt Jr. was racing in the Xfinity race for his only race of the year before moving to the NBC booth for the Cup race later Saturday. Earnhardt won NASCAR’s first Cup race back when the series resumed after the week off for 9/11.

Earnhardt, who had also lost his father in February of that year, held the American flag out his car window during the celebratory burnouts in an image associated with the sport and its 9/11 tributes.

“I feel kind of connected to that date because of what happened in our sport when we went back to Dover and with what was going on in my own life that year,” Earnhardt Jr. said Friday. “It was a very challenging year. I think it’s important that we continue to remember and honor everyone affected by (9/11) all these years later.”

On Sept. 11, 2001, IndyCar was already in Germany (as the CART Series) preparing for its weekend race — and was the only U.S.-based series to compete that weekend. On Saturday at Portland International Raceway, the teams were summoned to the grid for a 15-second moment of silence.

The attention turns to the baseball diamond Saturday night, when the Mets host the Yankees. It’s the first time the Subway Series has overlapped with Sept. 11.

Bobby Valentine, who managed the Mets in 2001, planned to throw a ceremonial first pitch to Joe Torre, the Yankees’ skipper at the time. Mike Piazza and more than a dozen other Mets players from the 2001 team are also expected to attend. Piazza memorably hit a go-ahead homer for the Mets on Sept. 21, 2001, in the team’s first game back at Shea Stadium.