Not necessarily. Some flights on small planes that serve small airports don't make their passengers go through TSA screening. Lots of airports in Alaska, for example, don't have TSA checkpoints. Of course, if they arrive in ANC and the passenger is making a connection on DL, AA, UA, or the like, they have to go through screening in ANC. This is also true for some flights in the lower 48--as one example, 9K (Cape Air) flights from MVY to EWB (Martha's Vineyard, MA to New Bedford, MA) have typically not required their passengers to go through security.