as ISR, unmanned systems, undersea warfare, precision strike, secure communications, missile defense and space programs, electronic warfare, aircraft readiness and the ability to project power in denied environments. (For more information on the risks and uncertainties related to our U.S. Government contracts, see Part I — Item 1A — Risk Factors in our Annual Report on Form 10-K for the year ended December 31, 2016).
International and Commercial Markets
Sales to end customers other than the U.S. Government represented 27% of our 2016 sales. These sales are generally affected by global economic conditions, geopolitical and security conditions and commodity prices, as well as our competitive success in winning new business and increasing market share. We believe that L3 will benefit from a large addressable international market with sales directly to foreign allied governments and under Foreign Military Sales (FMS) agreements between the U.S. Government and foreign governments. Although our international sales are experiencing near-term softness, we believe the focus of our international markets in areas such as ISR, simulators, communication systems, night vision products and sensor systems will benefit L3 in the long term. We also believe that the commercial markets in which we participate, such as aviation products, security and screening, simulation and training, and radio frequency microwave and power, have long term favorable fundamentals.
Key Performance Measures
The primary financial performance measures that we use to manage our businesses and monitor results of operations are (i) sales, (ii) operating income and (iii) net cash from operating activities (Operating Cash Flow). Management believes that these financial performance measures are the primary growth drivers for our earnings per share and cash flow per common share. Generally, in evaluating our businesses and contract performance, we focus on net sales, operating income, operating margin, which we define as operating income as a percentage of sales, and Operating Cash Flow, and not the type or amount of operating costs.
One of our primary business objectives is to increase sales organically and through select business acquisitions. We define organic sales as net sales excluding the sales impact of acquisitions and divestitures. Sales declines related to business divestitures are sales from divestitures that are included in our actual results for the twelve-month period prior to the divestitures. Sales increases related to acquired businesses are sales from acquisitions that are included in our actual results for less than twelve-month period. We expect to supplement, strengthen and enhance our existing businesses by selectively acquiring businesses that: (1) add important new technologies and products, (2) provide access to select customers, programs and contracts and (3) provide attractive returns on investment. Another important financial performance measure that we use is operating margin, because sales growth combined with operating margin levels determine our operating income levels. Operating Cash Flow is also an important financial performance measure because Operating Cash Flow measures our ability to convert operating income into cash after paying income taxes and interest expenses and investing in working capital.
Sales Trend.
For the quarter ended March 31, 2017 (2017 First Quarter), consolidated net sales of $2,669 million increased by $316 million, or 13%, compared to the quarter ended March 25, 2016 (2016 First Quarter). Organic sales increased by $270 million, or 11%, for the 2017 First Quarter. Organic sales exclude $51 million of sales increases related to business acquisitions and $5 million of sales declines related to business divestitures. See Results of Operations, including segment results below, for a further discussion of sales.
For the year ended December 31, 2016, our largest contract (revenue arrangement) in terms of annual sales was the Fort Rucker Maintenance Support contract with the U.S. Army Aviation and Missile Life Cycle Management Command (AMCOM), which is included in our Aerospace Systems segment. Under this contract, which generated approximately 4% of our sales in the 2017 First Quarter and for the year ended December 31, 2016, we provide maintenance, logistics and other related sustainment support services for rotary wing aircraft assigned to Fort Rucker and satellite units in Alabama. Our period of performance under this contract continues through September 30, 2017. We are one of several contractors expected to bid on the re-competition of this contract and expect an award decision in the second half of 2017.
We derived approximately 70% of our 2016 sales from DoD customers, and, as a result, our sales are highly correlated to DoD budget levels. DoD budgets are a function of several factors and uncertainties beyond our control, including, but not limited to, changes in U.S. procurement policies, budget considerations, current and future economic conditions, presidential administration priorities, U.S. military engagements, changing national security and defense requirements, geo-political developments, actual fiscal year congressional appropriations for defense budgets, and sequestration and other DoD budget reductions. Any of these factors could result in a significant