< PrevNext > 37. Northrop Grumman Falls Church, Va. Share 2016 U.S.-Booked Air Volume: $110 millionPrincipal Air Suppliers: American, Delta, UnitedPrincipal Hotel Suppliers: Hilton, InterContinental, MarriottPrincipal Car Rental Suppliers: Avis, BudgetPrincipal Card Supplier: JPMorgan Chase VisaPrincipal Online Booking Tool: ConcurPrincipal Expense Supplier: ConcurConsolidated/Primary Global TMC: BCD TravelAccording to BTN's estimate, Northrop Grumman's 2016 U.S.-booked air volume increased 3 percent year over year to $110 million. The defense contractor and global security company's sales revenue increased 4 percent year over year by $982 million, owing to higher sales in both its aerospace systems and missions systems businesses. Operating income also increased 4 percent, owing to a $137 million reduction in unallocated corporate expenses and to higher sales volume. Operating costs increased 2 percent to $21.3 billion. At the end of 2016, Northrop Grumman's backlog, an indicator of demand, totaled $45.3 billion, a 26 percent year-over-year increase, of which $18.3 billion is expected to turn into 2017 sales revenue. The company employed 67,000 at the end of 2016, up 2,000 employees from the previous year.