Navistar International (NYSE: NAV) makes commercial trucks and diesel engines. The company's largest customer is Ford, which buys PDQ for its XYZ, accounted for 9% of total revenues in 2009, a significant amount for a single customer. As a result of its focus on trucks, NAV grew rapidly when trucks became popular consumer vehicles, but has been hit hard by the increase in gasoline prices from.
Navistar also has a healthy business building military vehicles. Since 2006, the company has secured over $5 billion in government orders for military trucks and vehicles. Examples of contracts won is a $752 million contract to improve the Mine Resistant Ambush Protected (MRAP) vehicle.
NAV's net sales declined sharply in 2009. Between 2008 and 2009, NAV's total revenues declined from $14.7 billion in 2008 to $11.6 billion in 2009. However, despite this decrease in revenues, NAV's net income increased from $134 million in 2008 to $320 million in 2009. The company was able to increase its profitability in large part by cutting down on its expenses and thereby increasing its operating income.
Navistar's Truck Segment makes medium-duty and heavy-duty trucks and buses (Class 4 to 8). It is Navistar's largest business segment, accounting for 63.1% of consolidated net sales.  In 2009, this segment posted total sales of $7.3 billion.
The Engine Segment makes diesel engines used for the company's medium- and heavy-duty trucks and school buses. Navistar's products are sold mainly in North and South America and to other Original Equipment Manufacturers (OEMs) under the MaxxForce brand name. Navistar provides all of Ford's diesel-powered, super-duty trucks and vans. In 2009, this segment posted total revenues of $2.7 billion.
The Parts Segment provides engine parts to support the company's production of trucks, school buses and military vehicles, in addition to Navstar's OEM customers. In 2009, this segment posted total revenues of $2.2 billion.
Navistar's Financial Services Segment provides wholesale, retail and lease financing of products sold by Navistar and other truck manufacturers. This segment posted total revenues of $348 million in 2009.
Stricter governmental regulations on engine emissions in the US were released, increasing Navistar's cost of truck and engine production. In addition, Navistar also faces strict noise and safety regulations. As these regulations become more stringent, Navistar's trucks and engines have to be emission- and noise- compliant to remain in business. As a result, Navistar has incurred increasing research and development costs and which has lowered the margin earned on sales.  In addition, the truck market anticipated the increasing prices due to stricter standards, pushing them to purchase trucks, buses and engines up to two years in advance. Overall, Navistar's sales declined 13% in 2007 as emission-compliant vehicles entered the market. 
Navistar has received over $5 billion in contract orders since 2006, primarily from the US Marine Corps and the US Army. The company is the largest supplier of Mine Resistant Ambush Protected (MRAP) vehicles to the US military. Navistar has been awarded several significant contracts to produce armored vehicles. In particular, the company won a $1.3 billion contract over several years, providing tactical vehicles for Afghanistan and Iraq in May. Navistar also won a $752 million contract to produce a lighter MRAP vehicle. The US government is one of Navistar's more stable customers. As it's share in Navistar's sales continues to increase, the stability in the company's sales increase as well. This is unlike Ford (currently Navistar's largest customer) which is subject to economic and market volatility.
Navistar has a number of major competitors in the US. Navistar competes with these OEMs in the production of medium- and heavy-duty trucks and buses, which account for about 60 percent of the company's sales. Competitors include Daimler AG (DAI), AB Volvo (VOLVY), and PACCAR (PCAR).