Can you get from Seattle downtown to the museam of flight or the boeing factory by public transport?

As others have mentioned, the Metro line #174 provides service between Downtown Seattle & the museum of flight. If you are trying to also get to the Boeing Factory where they offer tours by reservation, that is located in Everett and can be reached by taking Sound Transit bus #510 or 513 from Downtown Seattle to the Everett Station and transfering to an Everett transit local bus from there to the factory. Good Luck!