Exhibit 5

                                 August 3, 2001

Swift Transportation Co., Inc.
220 South 75th Avenue
Phoenix, Arizona 85043

      Re:   Registration Statement on Form S-8

Ladies and Gentlemen:

     We have  acted as  counsel  to Swift  Transportation  Co.,  Inc.,  a Nevada
corporation   (the   "Company"),   in  connection  with  the  preparation  of  a
Registration  Statement on Form S-8 to be filed with the Securities and Exchange
Commission  (the  "Registration  Statement"),  with respect to the  registration
under the Securities Act of 1933, as amended, of 269,569 shares of the Company's
common  stock,  par value  $.001 per share (the  "Shares"),  subject to issuance
under the M.S. Carriers, Inc. Retirement Savings Plan (the "Plan").

     We have examined the  Registration  Statement,  the  Company's  Articles of
Incorporation  and  Bylaws,  as  amended,  and such  other  documents,  records,
certificates,  memoranda,  and other instruments as we deem necessary as a basis
for this  opinion.  We have  assumed the  genuineness  and  authenticity  of all
documents  submitted  to us as  originals,  the  conformity  of originals of all
documents submitted to us as copies thereof,  and the due execution and delivery
of all  documents  where due execution  and delivery are a  prerequisite  to the
effectiveness thereof.

     We express no opinion as to the  applicability or compliance with or effect
of federal  law or the law of any  jurisdiction  other  than the Nevada  General
Corporation Law.

     Based upon our  examination,  subject to the  assumptions  stated above and
relying on the  statements  in the  documents  we have  examined,  we are of the
opinion that any  original  issuance  Shares that may be issued  pursuant to the
Plan have been duly  authorized and, when issued in accordance with the terms of
the Plan and upon receipt of the consideration  required thereby,  such original
issuance Shares will be validly issued, fully paid and nonassessable.

     We hereby  consent  to the  filing of this  opinion  as an  exhibit  to the
above-referenced  Registration  Statement and to the use of our name wherever it
appears  in the  Registration  Statement.  In  giving  such  consent,  we do not
consider  that we are  "experts"  within the meaning of such term as used in the
Securities  Act of  1933,  as  amended,  or the  rules  and  regulations  of the
Securities and Exchange  Commission issued thereunder,  with respect to any part
of  the  Registration  Statement,  including  this  opinion  as  an  exhibit  or
otherwise.

                                        Very truly yours,

                                        /s/ Snell & Wilmer L.L.P.
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                                        SNELL & WILMER L.L.P.