Between the 1999 through 2001 seasons , the NFL had an odd number of teams , 31 , as a result of the Cleveland Browns re-entering the league . Each week during these three seasons featured at least one team with its bye week ( the 2001 season also added an additional impromptu league-wide bye the weekend after the September 11 attacks ) . The league returned to having an even number of teams ( 32 ) in the 2002 season with the addition of the Houston Texans , and implemented the current bye week system
September 11 attacks
September 11 attacks
Bye (sports)