It's not technically predatory, in the legal/economic sense of the word. I would let "extortionary" slide because they are exploiting a de facto monopoly on the route and they are pricing what the market will sustain for the limited service-- x seats at $x. When a competitor moves into the market, it may change to 2x at $x/3, but that competitor needs to show up first.
Predatory is what NW does: when a competitor moves into a market, undercut them so severely they need to close up shop, then raise them back again.