While many US-based teams in basketball, hockey and baseball have their owner's team aircraft, seats are still given on a seniority basis. In 2008, Northwest started a 10-year agreement with the NBA in which seven A319s were configured to how they wanted with the process the same. These planes have 54 first class chairs.
Example: The plane for the New Orleans Hornets circa 2006
http://www.okctalk.com/showthread.php?t=13757&page=1
For American football (gridiron), the charter is a standard commercial aircraft and the seniority priority still applies.