Two players who wear No. 26 joined hands with the coaches of the St. Louis Rams and Minnesota Vikings in tribute to the victims of the school massacre in Newtown, Conn.
The moment of silence before Sunday's game included coaches Jeff Fisher of St. Louis and Leslie Frazier of Minnesota, along with Rams running back Daryl Richardson and Vikings cornerback Antoine Winfield.
The players were selected because their number represents the number slain at Sandy Hook Elementary School on Friday.
Dozens of children wearing uniform jerseys held hands with players in a circle extending from the 30-yard lines at the Edward Jones Dome, centered on the Rams logo at midfield. Richardson, Winfield and the coaches formed an inner circle.
Flags were at half-staff at M&T Bank Stadium when the Baltimore Ravens hosted the Denver Broncos in one of the eight early games.
With the Maryland National Guard standing on the opposite end of the field from the flag bearers, the scoreboards went black as the public address announcer asked the crowd to observe "silent reflection" in the wake of Friday's "horrific tragedy."
Players from both team stood stoically on the sideline. The moment of silence was followed by the national anthem.
In New Orleans, the Superdome fell silent for nearly 30 seconds before the Saints hosted Tampa Bay. People around the stadium removed their hats, bowed their heads and remained still until the public address announcer introduced the national anthem singer, "American Idol" contestant Skylar Laine.
In Houston, video screens went black as the moment was observed before the Texas hosted the Indianapolis Colts.
In Chicago, Green Bay wide receiver Donald Driver retweeted the names of the victims.
Buffalo Bills CEO Russ Brandon tweeted that a moment of silence was to be held in Toronto later Sunday before the Bills played the Seattle Seahawks at the downtown Rogers Centre.