Originally Posted by
ijgordon
Not sure why you bring up upgrades, but E was historically used to determine if confirmed flight change was allowed. OP suggests that may have changed. If so, it could certainly make something like ExpertFlyer less useful for monitoring availability of CFC.
ehhh just misunderstood what CFC means. I can see why AA used the E bucket, it represents the most restricted seats in the cabin (the ones given out for employee travel). AA probably came up with a more efficient formula than relying on the seats in the E bucket.