In its final two years of existence the AFL had ten teams, grouped into two divisions. Each team played a home-and-away game against the other four teams in its division, a home-and-away series against one of the five teams in opposite division, and one game each against the remaining four teams from the opposite division. Interestingly, using that format, the defending World ChampionNew York Jets went 10-0 against the five teams they played twice (i.e., their four weak divisional rivals plus last-place second-year Cincinnati) while going 0-4 against the top four teams in the West.
For the 1969 season, a provision was made for a four team playoff to determine the AFL Champion, the league's representative in the Super Bowl, with the #1 team in the division to play against the #2 team in the opposite division. The NFL also had a four team playoff, introduced in 1967, matching the winners of the Capitol and Century divisions, and the Coastal and Central divisions.
The 1970 merger placed the 10 AFL teams (along with 3 teams from the pre-1970 NFL) into the 13-team AFC. (The other NFL teams went into the 13-team NFC.)