Knight-Swift Transportation (KNX) 8-K Departure of Directors or Certain Officers

Exhibit 99.1

William J. Post

February 18, 2014

Board of Directors

Swift Transportation Company

2200 S. 75^th Avenue

Phoenix, Arizona, 85043

Dear Directors,

Please accept this letter as recognition of my intention to not run for reelection as a Director of Swift Transportation Company in the 2014 Annual Meeting. Over the last 3 years it has been my pleasure to work with you, as well as the entire management team of Swift, and I wish all of you the very best in the future.

Thank you for the opportunity to serve.

Sincerely,

/s/ William J. Post

William J. Post

Chairman and Director

Swift Transportation Company