Well, since there was no reply, let me resurrect this thread from the dead, because I would like the same feature. If I can get alerts for ALL flights to/from a given airport, why not allow the smaller subset of all flights by a given operator to/from a specific airport?
When logged in, click on the My Alerts link on the top of the page. Setup a new alert and check the box for Advanced Options. From there you can enter in the origin and/or destination of your choosing. Once you click Setup Alert you’re good to go!