The components of long-term debt (net of discounts), along with maturity dates for the years subsequent to May 31, 2013, are as follows (in millions):

				May 31,
				2013		2012
Senior unsecured debt:
	Interest Rate %		Maturity
	9.65		2013	$	-	$	300
	7.38		2014		250		250
	8.00		2019		750		750
	2.625		2023		499		-
	2.70		2023		249		-
	3.875		2043		493		-
	4.10		2043		499		-
	7.60		2098		239		239
	Total senior unsecured debt				2,979		1,539
Capital lease obligations					11		128
					2,990		1,667
		Less current portion			251		417
				$	2,739	$	1,250

Interest on our fixed-rate notes is paid semi-annually. Long-term debt, exclusive of capital leases, had estimated fair values of $3.2 billion at May 31, 2013 and $2.0 billion at May 31, 2012. The estimated fair values were determined based on quoted market prices and the current rates offered for debt with similar terms and maturities. The fair value of our long-term debt is classified as Level 2 within the fair value hierarchy. This classification is defined as a fair value determined using market-based inputs other than quoted prices that are observable for the liability, either directly or indirectly.

We have a shelf registration statement filed with the Securities and Exchange Commission that allows us to sell, in one or more future offerings, any combination of our unsecured debt securities and common stock.

In April 2013, we issued $750 million of senior unsecured debt under our current shelf registration statement, comprised of $250 million of 2.70% fixed-rate notes due in April 2023 and $500 million of 4.10% fixed-rate notes due in April 2043. We utilized the net proceeds for working capital and general corporate purposes. In July 2012, we issued $1 billion of senior unsecured debt under a then current shelf registration statement, comprised of $500 million of 2.625% fixed-rate notes due in August 2022 and $500 million of 3.875% fixed-rate notes due in August 2042. We utilized the net proceeds for working capital and general corporate purposes.

During 2013, we made principal payments of $116 million related to capital lease obligations and repaid our $300 million 9.65% unsecured notes that matured in June 2012 using cash from operations.

A $1 billion revolving credit facility is available to finance our operations and other cash flow needs and to provide support for the issuance of commercial paper. On March 1, 2013, we entered into an amendment to our credit agreement to, among other things, extend its maturity date from April 26, 2016 to March 1, 2018. The agreement contains a financial covenant, which requires us to maintain a leverage ratio of adjusted debt (long-term debt, including the current portion of such debt, plus six times our last four fiscal quarters' rentals and landing fees) to capital (adjusted debt plus total common stockholders' investment) that does not exceed 70%. Our leverage ratio of adjusted debt to capital was 51% at May 31, 2013. We believe the leverage ratio covenant is our only significant restrictive covenant in our revolving credit agreement. Our revolving credit agreement contains other customary covenants that do not, individually or in the aggregate, materially restrict the conduct of our business. We are in compliance with the leverage ratio covenant and all other covenants of our revolving credit agreement and do not expect the covenants to affect our operations, including our liquidity or expected funding needs. As of May 31, 2013, no commercial paper was outstanding, and the entire $1 billion under the revolving credit facility was available for future borrowings.

We issue other financial instruments in the normal course of business to support our operations, including standby letters of credit and surety bonds. We had a total of $538 million in letters of credit outstanding at May 31, 2013, with $128 million unused under our primary $500 million letter of credit facility, and $539 million in outstanding surety bonds placed by third-party insurance providers. These instruments are required under certain U.S. self-insurance programs and are also used in the normal course of international operations. The underlying liabilities insured by these instruments are reflected in our balance sheets, where applicable. Therefore, no additional liability is reflected for the letters of credit and surety bonds themselves.