Those who are interested in eventually becoming the principal player in their section must climb to the top through a series of challenges. This is done at the discretion of the director. The order of challenges must be stepwise, meaning the last chair in a section cannot challenge the principal player without first challenging the other players in between his/her position and the principal chair.
A principal player cannot be challenged one month before a performance. On the same note, any challenge that may result in a switch in sections (i.e. Trumpet II to Trumpet I) also is not permissible one month before a concert.