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                                                                    EXHIBIT 31.A

                                  CERTIFICATION

I, John W. Somerhalder II, certify that:


         1. I have reviewed this annual report on Form 10-K of Colorado
         Interstate Gas Company;

         2. Based on my knowledge, this annual 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 annual report;

         3. Based on my knowledge, the financial statements, and other financial
         information included in this annual 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 annual report;

         4. The registrant's other certifying officer(s) 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)) 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) 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

                  (c) 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(s) 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: March 15, 2004

                                          /s/ John W. Somerhalder II
                                          --------------------------------------
                                          John W. Somerhalder II
                                          Chairman of the Board and
                                          Chief Executive Officer
                                          (Principal Executive Officer)
                                          Colorado Interstate Gas Company