Exhibit
        31.1
 **CERTIFICATION**
 
 I,
        Kevin
        P. Knight, 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:  May
        9,
        2006
 
 By:
              /s/
                  Kevin P. KnightChief
                  Executive Officer
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