Exhibit
      31.2


**CERTIFICATION**





I,
      David
      A. Jackson, certify that:





1.
            I
                have reviewed this quarterly report on Form 10-Q of Knight Transportation,
                Inc.;





2.
            Based
                on my knowledge, this report does not contain any untrue statement
                of a
                material fact or omit to state a material fact necessary to make
                the
                statements made, in light of the circumstances under which such statements
                were made, not misleading with respect to the period covered by this
                report;




3.
            Based
                on my knowledge, the financial statements, and other financial information
                included in this report, fairly present in all material respects
                the
                financial condition, results of operations and cash flows of the
                registrant as of, and for, the periods presented in this
                report;





4.
            The
                registrant's other certifying officer and I are responsible for
                establishing and maintaining disclosure controls and procedures (as
                defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal
                control over financial reporting (as defined in Exchange Act Rules
                13a-15(f) and 15d-15(f)) for the registrant and
                have:




(a)  Designed
      such
      disclosure controls and procedures, or caused such disclosure controls and
      procedures to be designed under our supervision, to ensure that material
      information relating to the registrant, including its consolidated subsidiaries,
      is made known to us by others within those entities, particularly during the
      period in which this report is being prepared;





(b)  Designed
      such
      internal control over financial reporting, or caused such internal control
      over
      financial reporting to be designed under our supervision, to provide reasonable
      assurance regarding the reliability of financial reporting and the preparation
      of financial statements for external purposes in accordance with generally
      accepted accounting principles;





(c)  Evaluated
      the
      effectiveness of the registrant's disclosure controls and procedures and
      presented in this report our conclusions about the effectiveness of the
      disclosure controls and procedures, as of the end of the period covered by
      this
      report based on such evaluation; and





(d)  Disclosed
      in
      this report any change in the registrant's internal control over financial
      reporting that occurred during the registrant's most recent fiscal quarter
      (the
      registrant's fourth fiscal quarter in the case of an annual report) that has
      materially affected, or is reasonably likely to materially affect, the
      registrant's internal control over financial reporting; and





5.
            The
                registrant's other certifying officer and I have disclosed, based
                on our
                most recent evaluation of internal control over financial reporting,
                to
                the registrant's auditors and the audit committee of the registrant's
                board of directors (or persons performing the equivalent
                functions):




(a)  All
      significant deficiencies and material weaknesses in the design or operation
      of
      internal control over financial reporting which are reasonably likely to
      adversely affect the registrant's ability to record, process, summarize and
      report financial information; and





(b)  Any
      fraud,
      whether or not material, that involves management or other employees who have
      a
      significant role in the registrant's internal control over financial
      reporting.





Date:  November
      8, 2006





By:
            /s/
                David A. JacksonDavid
                A. Jackson
              Chief
                Financial Officer




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      to Form 10-Q