**EXHIBIT 31.A****CERTIFICATION**I, James J. Cleary, certify that:1. I have reviewed this Annual Report on Form 10-K of Colorado Interstate Gas Company;2. Based on my knowledge, this report does not contain any untrue statement of a materialfact or omit to state a material fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading with respect to theperiod covered by this report;3. Based on my knowledge, the financial statements, and other financial information includedin this report, fairly present in all material respects the financial condition, results ofoperations and cash flows of the registrant as of, and for, the periods presented in thisreport;4. The registrant’s other certifying officer(s) and I are responsible for establishing andmaintaining 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 ActRules 13a-15(f) and 15d-15(f)) for the registrant and have:(a) Designedsuch disclosure controls and procedures, or caused such disclosure controlsand procedures to be designed under our supervision, to ensure that material informationrelating to the registrant, including its consolidated subsidiaries, is made known to us byothers within those entities, particularly during the period in which this report is beingprepared; and(b) Designed suchinternal control over financial reporting, or caused such internalcontrol over financial reporting to be designed under our supervision, to providereasonable assurance regarding the reliability of financial reporting and the preparation offinancial statements for external purposes in accordance with generally acceptedaccounting principles; and(c) Evaluated theeffectiveness of the registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of the disclosure controlsand procedures, as of the end of the period covered by this report based on suchevaluation; and(d) Disclosedin this report any change in the registrant’s internal control over financialreporting that occurred during the registrant’s most recent fiscal quarter (the registrant’sfourth fiscal quarter in the case of an annual report) that has materially affected, or isreasonably likely to materially affect, the registrant’s internal control over financialreporting.5. The registrant’s other certifying officer(s) and I have disclosed, based on our mostrecent evaluation of internal control over financial reporting, to the registrant’s auditorsand the audit committee of the registrant’s board of directors (or persons performing theequivalent functions):(a) All significant deficiencies and material weaknesses in the design or operationof internal control over financial reporting which are reasonably likely toadversely affect the registrant’s ability to record, process, summarize and reportfinancial information; and(b) Any fraud, whether or not material, that involves management or other employeeswho have a significant role in the registrant’s internal control over financialreporting.Date:March 4, 2008         */s/ James J. Cleary*   James J. Cleary   President