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Why Is Sea-Tac Airport Shaped Like a Boomerang?

COVID-19 and travel at SEA Airport More Information

July 15, 2019

Did you know that the Sea-Tac Airport terminal is shaped somewhat like a boomerang? 

Want to know why? It isn’t just because of the obvious aesthetic appeal of the shape, or as a subtle reminder to make sure people keep coming back! 

The reason dates to the original configuration of the first runways which were constructed between 1943 and 1944. Sea-Tac, like many military airports in the World War II era, was constructed with runways heading in different directions to cover all wind conditions. The airport started with four runways: the north/south, the two arms of the “X”, and the east/west. The terminal building was built in its unique boomerang shape to fit into this runway configuration, as you can see from this 1948 aerial photo.  

Aerial shot of Sea-Tac 1948

As commercial aviation technology and practices developed over the years, the need for the east/west runway depreciated. Starting in the 1960’s the original T and X runways/taxiways were replaced by the current three parallel runways situated on a north/south axis. 

Though the runway configuration might have changed over the years (see the photos below) you can see how the current Sea-Tac terminal keeps the general shape of the original terminal building to this day.


Aerial shot of Sea-Tac 1961


Sea-Tac Aerial 1965


Sea-Tac Aerial 2018

Quick Facts about the Runways:

1. Sea-Tac has three runways

  • The center runway, 16C/34C, was originally built in 1969 and was reconstructed in 2009 and is 9,426’ long
  • 16L/34R is the longest runway at 11,901’ and was reconstructed in 2009 
  • 16R/34L was completed  in 2008 and is 8,500’ long

2. What the heck do the number/letters mean anyway? 

  • The numbers that designate a runway are determined by the runway’s heading in the magnetic azimuth (compass bearing) in which a runway is oriented to the nearest 10 degrees and truncating the last digit, meaning runways are numbered from 1 to 36 
  • Each runway will have two separate numerical designations based on which direction the aircraft is approaching or taking off (i.e., 16L in south flow, and 36R for northflow; thus the runway in shorthand would be called 16L/34R)
  • The letters "L” and "R” designate the relative position (left or right) of each runway respectively when approaching. Since Sea-Tac has three parallel runways the “C” stands for center. See the diagram below.

Sea-Tac runways diagram with names and feet

Learn more about Sea-Tac’s runways 


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