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.