Originally Posted by Andrew Yiu

All SEs (those who are actually SEs, not companions or nominees of SE) who are on the day of departure waitlist would clear before any Es are cleared regardless of fare paid, connections, check in time etc. Sometimes things are not the way it appears to be - for example, an E might be paged up for the last J seat over a SE on standby for J because they are paid J confirmed on a later flight.