HT to The Flight Deal for sharing a cheap fare between Portland and Boston on Alaska Airlines for just $238. Although it’s a nonstop flight so the CPM is higher than my usual goal of 4 cents per mile, often this is close to as good as it gets for this carrier (no stops means no adding connections for extra miles at the same price). However, I did play around with it, and there are lots of things you can do to make this deal suit your own needs. For example, depart from Seattle and you can save even more by paying only $218 (4.4 CPM).
Or, American Airlines and United Airlines have comparable fares that connect in places like DFW, SFO, and IAH. Although you’ll pay closer to $260, the added distance brings the CPM down to 4.1 CPM (American) or 3.9 CPM (United).
Hopefully these examples demonstrate how to take news about one sale on a particular route or carrier and explore other options. Often airlines will lower their prices to remain competitive with a competitor, or in cases like Portland and Seattle there may be very similar fares from either city to the same destination.