The Boeing 737-800 is a stretched version of the 737-700. It replaced the 737-400. The Boeing 737-800 competes with the Airbus A320. The 737-800 seats 162 passengers in a two-class layout or 189 passengers in a one-class layout. The 737−800 was launched by Hapag-Lloyd Flug (now TUIfly) in 1994 and entered service in 1998.
Following Boeing's merger with McDonnell Douglas, the 737-800 also filled the gap left by Boeing's decision to discontinue the McDonnell Douglas MD-80 and MD-90 aircraft. For many airlines in the U.S., the 737-800 replaced aging Boeing 727-200trijets.
The 737-800 burns 850 US gallons (3,200 L) of jet fuel per hour—about 80 percent of the fuel used by an MD-80 on a comparable flight, while carrying more passengers. According to the Airline Monitor, an industry publication, a 737-800 burns 4.88 US gallons (18.5 L) of fuel per seat per hour. In 2011, United Airlines— flying a Boeing 737-800 from Houston to Chicago—operated the first U.S. commercial flight powered by a blend of algae-derived biofuel and traditional jet fuel to reduce its carbon footprint.
In early 2017, a new 737-800 was valued at $48.3 million, falling to below $47 million by mid-2018. By 2025, a 17-year-old 737-800W will be worth $9.5 million and leased for $140,000 per month.
As of May 2019, Boeing had delivered 4,979 737-800s, 116 737-800As, and 21 737-800 BBJ2s and has 12 737-800 unfilled orders. The 737-800 is the most popular variant of the 737NG and ranks as the most common narrow-body aircraft in service. Ryanair, an Irish low-cost airline, is among the largest operators of the Boeing 737-800, with a fleet of over 400 737-800 aircraft serving routes across Europe, Middle East and North Africa.