Seattle-Tacoma International Airport will close its middle runway today. The 41-year-old runway will remain closed for repairs for 60 days while construction crews replace 150 deteriorating concrete panels.
Those replacements are designed to keep the runway in good operating condition until 2016 when it is scheduled to be replaced.
The concrete in those panels is spalling and cracking. That damage raises the possibility that pieces of concrete could break loose and damage aircraft and their engines.