Can someone identify this unusual plane at SeaTac airport?
There is a big clue right underneath the "Sea-Tac Airport" decal - it says


  FIRE RESCUE


It can be seen a little better on this image


source: wikimedia commons

It is a rig used for fire and evacuation training.


  A unique tool the department uses is an aircraft mock-up designed for aircraft approach, entry and tactics training on the airfield. The smoke generated is not harmful to the environment and provides a realistic challenge.
  source: https://www.portseattle.org/page/training


The image below appears to show it in use: