The Boeing 737 and its many variants is the mainstay of Alaska Airlines' fleet. Alaska Airlines has more than 50 of these Boeing B737-800s (IATA aircraft code 73H), making it the most numerous aircraft in its fleet by some margin.
Each Alaska Airlines Boeing B737-800 has 157 seats, with 141 in economy class and 16 in First. While the -800 is Alaska's most numerous aircraft, it is not its largest. The -900 has 12 more seats in economy class, or four extra rows.
Alaska Airlines has two different configurations of B737-800. This one has an extra toilet in the aft of the aircraft, where seats 30A, 30B and 30C should be.