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Why Is SEA Airport Shaped Like a Boomerang?

July 15, 2019

Did you know that the Seattle-Tacoma International Airport (SEA) 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, 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 airport 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 Airport 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 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 Airport runways 


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