As per
mersk862 and
jjgollum, (edit BOS TSA Elite Screening)
With the BOS terminal, the elite line can be lengthy at times, since besides the CO EliteAccess customers, DL also allows Gold/Platinum Medallions (which there are a good amount of at BOS), Crown Room members and Delta Shuttle customers to use the First Class line - in the mornings it can back up a decent bit.