Seniority is one of the main components of the unions. However the pilots union is different from most in that they don't keep "comprehensive" seniority lists across company lines.

In other unions, "locals" are regional shops which "farm out" members to local companies at set wages. Members make the same amount of money regardless of who they are working for and wages are set at a regional level with consideration to national trends.

In the pilot union "locals" are "company shops" and only represent pilots at one employer. Wages are set at the local level with consideration to national trends.