NOT IN lists are transformed into multiple predicates that use the <> operator. <> predicates are not optimizable, but they are sargable (See ). For example: orig_airport NOT IN ('ABQ', 'AKL', 'DSM')

becomes orig_airport <> 'ABQ' AND orig_airport <> 'AKL' AND orig_airport <> 'DSM'

In addition, large lists are sorted in ascending order for performance reasons.