Exhibit 32.2


                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

         In connection with the Annual Report of AAON, Inc. (the "Company"), on
Form 10-K for the year ended December 31, 2007, as filed with the Securities and
Exchange Commission on the date hereof (the "Report"), I, Kathy I. Sheffield,
Chief Financial Officer of the Company, certify, pursuant to 18 U.S.C. ss. 1350,
as adopted pursuant to ss. 906 of the Sarbanes-Oxley Act of 2002, that:

         (1) The Report fully complies with the requirements of section 13(a) or
15(d) of the Securities Exchange Act of 1934; and

         (2) The information contained in the Report fairly presents, in all
material respects, the financial condition and result of operations of the
Company.



March 11, 2008                                    /s/ Kathy I. Sheffield
                                                  -------------------------
                                                  Kathy I. Sheffield
                                                  Chief Financial Officer