The oldest part of their fleet are B734's of which they have 5 (plus I think some Combi's which only service Alaska) all of those are due to be gone by the end of 2017. The rest of their fleet is B737/B738/B739's - all but 30 are B738/B739's.

In fact among legacy carriers Alaska has the youngest fleet age of any of them. Alaska also has excellent on-time and baggage performance - among the best, if not the best in the industry.