Age and price vary on each airline's unaccompanied minors policy, SEA Airport suggests contacting your airline in advance to see what their exact policies are. Allow extra time for check in and paperwork required before the flight.
Escorting Minors to Their Gate
Unfortunately, due to COVID-19, we don't have an estimated re-opening or start date for our SEA Visitor Pass Program and we truly apologize. At this time the only way to get a gate pass is by contacting your airline directly. Each airline has their own policies, but usually will approve a gate pass if you are assisting unaccompanied minors. Airlines will usually allow for a parent or guardian to enter and go through security with them and will assign you a gate pass during the booking process.
According to TSA, IDs for security screening need to be government-issued with a photo to help confirm your identity. TSA does not require people under 18 to provide identification when traveling within the United States. Usually airlines don't require a form of ID for boarding and just require your boarding pass.