WHERE orig_airport = 'SFO'
WHERE lower(orig_airport) = 'sfo'
References to contiguous columns in other predicates in the statement when there is a multi-column index can further define the starting or stopping points. (If the columns are not contiguous with the first column, they are not optimizable predicates but can be used as qualifiers.) For example, given a composite index on FlightAvailability (flight_id, segment_number, and flight_date), the following predicate satisfies that condition:
WHERE flight_id = 'AA1200' AND segment_number = 2
WHERE flight_id = 'AA1200' AND flight_date = CURRENT_DATE