TULSA, OK--(Marketwire - August 13, 2009) - AAON, INC. (NASDAQ: AAON), a leading manufacturer of heating and cooling products, is pleased to announce that it has been added to Standard & Poor's SmallCap 600 Index. AAON will be added to the S&P SmallCap 600 GICS Building Products Sub-Industry index.

AAON will replace Informatica in the S&P SmallCap 600, Informatica Corp. will replace FMC Corp. in the S&P MidCap 400, and FMC Corp. will replace Centex Corp. in the S&P 500 after the close of trading on Tuesday, August 18. Centex Corp. is being acquired by S&P 500 constituent Pulte Homes Inc. in a deal expected to close on or about that date.

About Standard & Poor's Index Services

Standard & Poor's Index Services, the world's leading index provider, maintains a wide variety of investable and benchmark indices to meet an array of investor needs. Over $1 trillion is directly indexed to Standard & Poor's family of indices, which includes the S&P 500, the world's most followed stock market index, the S&P Global 1200, a composite index comprised of seven regional and country headline indices, the S&P Global BMI, an index with approximately 11,000 constituents, and the S&P GSCI, the industry's most closely watched commodities index. For more information, please visit www.standardandpoors.com/indices.

About AAON

AAON is engaged in the engineering, manufacturing, marketing and sale of air conditioning and heating equipment consisting of standard, semi-custom and custom rooftop units, chillers, boilers, air handling units, make-up air units, heat recovery units, condensing units and coils. Since the founding of AAON in 1988, AAON has maintained a commitment to design, develop, manufacture and deliver heating and cooling products to perform beyond all expectations and demonstrate the value of AAON to our customers. For more information, please visit www.aaon.com.

Contact Information: Contact: Jerry R. Levine Phone: (914) 244-0292 Fax: (914) 244-0295