contractual commitments we have contractual obligations and commitments in the form of capital leases , operating leases , debt obligations , purchase commitments , and certain other liabilities . we intend to satisfy these obligations through the use of cash flow from operations . the following table summarizes the expected cash outflow to satisfy our contractual obligations and commitments as of december 31 , 2010 ( in millions ) : .
what percentage of total expected cash outflow to satisfy contractual obligations and commitments as of december 31 , 2010 are due in 2013?
our capital lease obligations relate primarily to leases on aircraft . capital leases , operating leases , and purchase commitments , as well as our debt principal obligations , are discussed further in note 7 to our consolidated financial statements . the amount of interest on our debt was calculated as the contractual interest payments due on our fixed-rate debt , in addition to interest on variable rate debt that was calculated based on interest rates as of december 31 , 2010 . the calculations of debt interest take into account the effect of interest rate swap agreements . for debt denominated in a foreign currency , the u.s . dollar equivalent principal amount of the debt at the end of the year was used as the basis to calculate future interest payments . purchase commitments represent contractual agreements to purchase goods or services that are legally binding , the largest of which are orders for aircraft , engines , and parts . as of december 31 , 2010 , we have firm commitments to purchase 20 boeing 767-300er freighters to be delivered between 2011 and 2013 , and two boeing 747-400f aircraft scheduled for delivery during 2011 . these aircraft purchase orders will provide for the replacement of existing capacity and anticipated future growth . pension fundings represent the anticipated required cash contributions that will be made to our qualified pension plans . these contributions include those to the ups ibt pension plan , which was established upon ratification of the national master agreement with the teamsters , as well as the ups pension plan . these plans are discussed further in note 5 to the consolidated financial statements . the pension funding requirements were estimated under the provisions of the pension protection act of 2006 and the employee retirement income security act of 1974 , using discount rates , asset returns , and other assumptions appropriate for these plans . to the extent that the funded status of these plans in future years differs from our current projections , the actual contributions made in future years could materially differ from the amounts shown in the table above . additionally , we have not included minimum funding requirements beyond 2015 , because these projected contributions are not reasonably determinable . we are not subject to any minimum funding requirement for cash contributions in 2011 in the ups retirement plan or ups pension plan . the amount of any minimum funding requirement , as applicable , for these plans could change significantly in future periods , depending on many factors , including future plan asset returns and discount rates . a sustained significant decline in the world equity markets , and the resulting impact on our pension assets and investment returns , could result in our domestic pension plans being subject to significantly higher minimum funding requirements . such an outcome could have a material adverse impact on our financial position and cash flows in future periods . the contractual payments due for 201cother liabilities 201d primarily include commitment payments related to our investment in certain partnerships . the table above does not include approximately $ 284 million of liabilities for .