position. Conversely, if our portfolio with counterparties is in a gain position, we may receive margin. Our future cash flows are impacted by the nature of our derivative contracts and the market price of the commodities underlying our derivative contracts. As a result of the significant decreases in crude oil prices during 

2014, the fair value of our hedge contracts were in a loss position at December 31, 2014 , resulting in $925 million of margin postings to counterparties.  

 

Timing of SkyMiles Sales. In December 2011, we amended our American Express agreements and agreed to sell $675 million of unrestricted 

SkyMiles to American Express in each December from 2011 through 2014. Pursuant to the December 2011 amendment, American Express purchased $675 million of unrestricted SkyMiles in each of 2012 and 2013 with the final payment in 2014 . The SkyMiles purchased in December 2014 are expected to be utilized by American Express in 2015.  

 

In 2008, we entered into a multi-year extension of our American Express agreements and received $1.0 billion from American Express for an advance purchase of restricted SkyMiles. The agreement, as modified, provided that our obligations with respect to the advance purchase would be satisfied as American Express used the purchased miles over a specified future period (“SkyMiles Usage Period”). During the SkyMiles Usage Period, which commenced in December 2011, American Express utilized SkyMiles valued at $333 million annually over three years instead of paying cash to 

Delta for SkyMiles used. In December 2013, we and American Express amended this agreement to allow American Express to use the remaining SkyMiles, valued at $285 million, immediately and without restriction. As of December 31, 2014, American Express had utilized the remaining SkyMiles associated with this advance purchase.  

 

Pension Contributions. We sponsor defined benefit pension plans for eligible employees and retirees. These plans are closed to new entrants and are frozen for future benefit accruals. Our funding obligations for these plans are governed by the Employee Retirement Income Security Act, as modified by the Pension Protection Act of 2006. In 2014, we contributed $917 million to our defined benefit pension plans, including $250 million above the minimum funding requirements. These contributions satisfied the required contributions for our defined benefit plans for 2014 on an accelerated basis. We contributed $914 million in 2013 , including $250 million above the minimum funding levels, and $697 million in 2012 to our defined benefit pension plans. We estimate the funding under these plans will total at least $950 million in 2015 , including $340 million above the minimum funding requirements.  

 

Profit Sharing. As discussed above, our broad-based employee profit sharing program provides that, for each year in which we have an annual pretax profit, as defined by the terms of the program, we will pay a specified portion of that profit to employees. In determining the amount of profit sharing, the program defines profit as pre-tax profit excluding profit sharing and special items, such as MTM adjustments and