Historically, Horizon has done very little hiring compared with the rest of the industry. From 2004-2016 we didn't hire anyone at all. We were in PDX and people were happy to stay. Since 2016 they hired about a dozen people.
With the move to SEA, attrition has started to increase. There was no pay increase associated with the move, and so people are finding they can't afford to live there. Seattle is incredibly expensive. A 1BR apartment in the SeaTac area is $1200 or more a month. Otherwise, expect to live 30+ miles from work to find something minimally affordable.
With regard to hiring, the long-timers at the top of the pay scale will probably either stay until normal retirement, or will only leave for Alaska. I expect that the bottom half of the seniority list will become much more of a rotating door. Uncharacteristic of the industry, we actually get a lot of internal hires at Horizon. The last class was a mix of internal/external. The class prior was all internal. Prior to that was all external. They prefer to hire internal when they can. And they get a lot of interest because of the perceived connection to Alaska.
There is no formal flow-thru to Alaska. It's a separate company, and you have to compete with everyone else. The last time Alaska hired (about a year ago) they offered interviews to any Horizon Dispatcher that applied. They ended hiring 2 Dispatchers, of which one came from Horizon. In the previous round of hiring, 3 (out of 5) came from Horizon.
That said, I don't expect to see Alaska hiring much in the short term future. They're put the brakes on growth about a year ago, and with the 737 Max debacle, are not taking any airplanes to my knowledge.
Bottom line is don't go to Horizon with the expectation of flowing to Alaska. Go to Horizon because you want to work for Horizon, or because you want to live in Seattle.
Alaska has changed their hiring preferences before, so take this with a grain of salt... however... Right now they have said unofficially that they will try to fill a certain percentage of their classes with QX dispatchers, though I am not sure what percentage they have in mind. We are expecting to have at least 1, if not 2 classes at AS in the next year in order to cover current staffing needs as well as a few expected retirements.