A St. Joseph, Mo. police officer supports a giant flag to commemorate the Sept. 11 anniversary, before an NFL football game between the Kansas City Chiefs and the San Diego Chargers in Kansas City, Mo., Sunday, Sept. 11, 2016. (AP Photo/Ed Zurga)

Fans wave flags as a tribute to the 9-11 anniversary before an NFL football game between the Indianapolis Colts and the Detroit Lions in Indianapolis, Sunday, Sept. 11, 2016.

The American Flag is displayed during the National Anthem before an NFL football game between the Indianapolis Colts and the Detroit Lions in Indianapolis, Sunday, Sept. 11, 2016. (AP Photo/R Brent Smith)

Green Bay Packers wide receiver Jordy Nelson (87) and wide receiver Randall Cobb (18) talk to a first responder while helping hold a giant flag over the field in memory of 9/11 before an NFL football game against the Jacksonville Jaguars in Jacksonville, Fla., Sunday, Sept. 11, 2016. (AP Photo/Phelan M. Ebenhack)

Fans during a tribute to the 9/11 anniversary before an NFL football game between the Indianapolis Colts and the Detroit Lions in Indianapolis, Sunday, Sept. 11, 2016. (AP Photo/Jeff Roberson)

A fan holds up an American flag during the second half of an NFL football game between the Philadelphia Eagles and the Cleveland Browns, Sunday, Sept. 11, 2016, in Philadelphia. (AP Photo/Matt Rourke)

Seattle Seahawks head coach Pete Carroll, left, shakes hands with U.S. Navy sailors at CenturyLink Field before an NFL football game between the Seahawks and the Miami Dolphins, Sunday, Sept. 11, 2016, in Seattle. (AP Photo/Elaine Thompson)

Jacksonville Jaguars tight end Ben Koyack's cleats are seen as he warms up before an NFL football game against the Green Bay Packers in Jacksonville, Fla., Sunday, Sept. 11, 2016.(AP Photo/John Raoux)

Former New York Mayor Rudy Giuliani stands on the field before an NFL football game between the New York Jets and the Cincinnati Bengals Sunday, Sept. 11, 2016 in East Rutherford, N.J. (AP Photo/Bill Kostroun)

Marines take part in a halftime tribute to 9/11 victims at an NFL football game between the Tennessee Titans and the Minnesota Vikings Sunday, Sept. 11, 2016, in Nashville, Tenn. (AP Photo/James Kenney)

Detroit Lions outside linebacker Kyle Van Noy (53) and defensive end Ezekiel Ansah (94) help first responders hold the flag during the National Anthem before an NFL football game between the Indianapolis Colts and the Detroit Lions in Indianapolis, Sunday, Sept. 11, 2016. (AP Photo/Jeff Roberson)

An Arlington, Texas, fire truck uses its ladder to hoist a large American flag over the field during a tribute ceremony remembering the Sept. 11, attack at half time of an NFL football game between the New York Giants and Dallas Cowboys on Sunday Sept. 11, 2016, in Arlington, Texas.

Umpire Fred Bryan holds a small American flag during the singing of the national anthem before an NFL football game between the Seattle Seahawks and Miami Dolphins Sunday, Sept. 11, 2016, in Seattle. (AP Photo/Elaine Thompson)

Former Dallas Cowboys player George Teague carries the American flag as he leads the team out of the tunnel for an NFL football game against the New York Giants on Sunday Sept. 11, 2016, in Arlington, Texas. Teague carried the flag for the Cowboys when play returned after the Sept. 11, attacks. (AP Photo/Ron Jenkins)

Philadelphia Eagles wide receiver Jordan Matthews, right, meets with Vice President Joe Biden before an NFL football game against the Cleveland Browns, Sunday, Sept. 11, 2016, in Philadelphia.

Fans wave a flag during the first half of an NFL football game Sunday, Sept. 11, 2016, in Houston. (AP Photo/Eric Christian Smith)

A police office holds one of the 69 flags representing the Maryland victims of the 9/11 attacks before an NFL football game between the Baltimore Ravens and the Buffalo Bills in Baltimore, Sunday, Sept. 11, 2016. (AP Photo/Patrick Semansky)

Houston Texans defensive end J.J. Watt (99) joins police officers and other first responders in holding a field-sized American flag before an NFL football game Sunday, Sept. 11, 2016, in Houston. (AP Photo/David J. Phillip)

Members of the Houston Police Department SWAT team serve as honorary captains and are introduced before an NFL football game Sunday, Sept. 11, 2016, in Houston. (AP Photo/David J. Phillip)

A giant flag is spread over the field at Arrowhead Stadium to commemorate Sept. 11, before an NFL football game between the Kansas City Chiefs and the San Diego Chargers in Kansas City, Mo., Sunday, Sept. 11, 2016.

Tampa Bay Buccaneers defensive tackle Gerald McCoy warms up with a 9/11 remembrance shirt on before the first half of an NFL football game between the Atlanta Falcons and the Tampa Bay Buccaneers, Sunday, Sept. 11, 2016, in Atlanta. (AP Photo/David Goldman)

Tampa Bay Buccaneers cornerback Johnthan Banks (27) watches a pregame 9/11 remembrance before the first half of an NFL football game between the Atlanta Falcons and the Tampa Bay Buccaneers, Sunday, Sept. 11, 2016, in Atlanta. (AP Photo/David Goldman)

Fans hold a banner before an NFL football game between the Philadelphia Eagles and the Cleveland Browns, Sunday, Sept. 11, 2016, in Philadelphia.

Members of the military hold an American Flag before the first half of an NFL football game between the Atlanta Falcons and the Tampa Bay Buccaneers, Sunday, Sept. 11, 2016, in Atlanta. (AP Photo/David Goldman)

A paratrooper arrives at Nissan Stadium before an NFL football game between the Tennessee Titans and the Minnesota Vikings, Sunday, Sept. 11, 2016, in Nashville, Tenn.

American flag cleats of Oakland Raiders long snapper Jon Condo (59) are seen before an NFL football game against the New Orleans Saints in New Orleans, Sunday, Sept. 11, 2016.

Vice President Joe Biden and Philadelphia Eagles head coach Doug Pederson hold an American flag before an NFL football game against the Cleveland Browns, Sunday, Sept. 11, 2016, in Philadelphia. (AP Photo/Matt Rourke)

Cleveland Browns' Joe Thomas waist run onto the field before an NFL football game against the Philadelphia Eagles, Sunday, Sept. 11, 2016, in Philadelphia. (AP Photo/Matt Rourke)

A police officer holds an American flag before an NFL football game between the Philadelphia Eagles and the Cleveland Browns, Sunday, Sept. 11, 2016, in Philadelphia. (AP Photo/Matt Rourke)

Service personnel carry an American flag before an NFL football game between the Philadelphia Eagles and the Cleveland Browns, Sunday, Sept. 11, 2016, in Philadelphia. (AP Photo/Matt Rourke)

New York Giants wide receiver Odell Beckham wears special cleats for 911 prior to an NFL football game against the Dallas Cowboys on Sunday, Sept. 11, 2016, in Arlington, Texas. (AP Photo/Michael Ainsworth)