Leasing has always been an important source of finance to carriers in the U.S. airline industry. In the 1960-1970s, many carriers employed a type of lease called a financial lease as an alternative source of funds to acquire aircraft. It had a major advantage over purchasing the aircraft. It was “off-the-balance sheet financing,” as the obligations under this type of lease appeared only in the footnotes to carrier balance sheets. Little use was made of short-term lease agreements during this period. The situation has changed radically over the past three decades. In 1976, the Financial Accounting Standards Board issued SFAS No. 13 defining specific criteria for capital leases that required the reporting of these “off-the-balance sheet financing” as both a leasehold asset and a long-term liability recorded under the long-term debt section of the balance sheet. In response, the air carriers substantially altered the way they finance airplanes. Carriers began to lease more and more of their aircraft, but they did so by structuring leases as shorter-term operating leases, which are not reported on companies’ balance sheets. By strategically violating the criteria for capital leases, the air carriers once again pushed the leases off the balance sheet. The purpose of this research is to demonstrate the switch in the characteristics of aircraft leasing and to quantify the effects of such leases on air carrier debt burdens. In the process it will be argued that “debt is debt” no matter how it is structured. The paper updates two research studies by the authors to 2008.