and foreign currency exchange rates. Market risk is the potential negative impact of adverse changes in these prices or rates on our Consolidated Financial Statements. In an effort to manage our exposure to these risks, we enter into derivative contracts and may adjust our derivative portfolio as market conditions change. We expect adjustments to the fair value of financial instruments to result in ongoing volatility in earnings and stockholders' equity.  

 

The following sensitivity analysis does not consider the effects of a change in demand for air travel, the economy as a whole or actions we may take to seek to mitigate our exposure to a particular risk. For these and other reasons, the actual results of changes in these prices or rates may differ materially from the following hypothetical results.  

 

Aircraft Fuel Price Risk  

 

Changes in aircraft fuel prices materially impact our results of operations. We actively manage our fuel price risk through a hedging program intended to reduce the financial impact from changes in the price of jet fuel. We utilize different contract and commodity types in this program and frequently test their economic effectiveness against our financial targets. We rebalance the hedge portfolio from time to time according to market conditions, which may result in locking in gains or losses on hedge contracts prior to their settlement dates .  

 

Our fuel hedge portfolio consists of options, swaps and futures. The hedge contracts include crude oil, diesel fuel and jet fuel, as these commodities are highly correlated with the price of jet fuel that we consume. Our fuel hedge contracts contain margin funding requirements. The margin funding requirements may cause us to post margin to counterparties or may cause counterparties to post margin to us as market prices in the underlying hedged items change. If fuel prices change significantly from the levels existing at the time we enter into fuel hedge contracts, we may be required to post a significant amount of margin. We may adjust our hedge portfolio from time to time in response to margin posting requirements.  

 

For the year ended December 31, 2014 , aircraft fuel and related taxes, including our regional carriers, accounted for $13.5 billion , or 35% , of our total operating expense. We recognized $2.0 billion of fuel hedge losses during the year ended December 31, 2014 , due to unfavorable MTM adjustments.  

 

The following table shows the projected cash impact to fuel cost assuming 20% and 40% increases or decreases in fuel prices. The hedge gain (loss) reflects the change in the projected cash settlement value of our open fuel hedge contracts at January 31, 2015 based on their contract settlement dates, assuming the same 20% and 40% changes.  

Interest Rate Risk  

 

Our exposure to market risk from adverse changes in interest rates is primarily associated with our long-term debt obligations. Market risk associated with our fixed and variable rate long-term debt relates to the potential reduction in fair value and negative impact to future earnings, respectively, from an increase in interest rates.  

 

At December 31, 2014 , we had $4.1