The Cessna 172 Skyhawk is a four-seat, single-engine, high-wing fixed-wing aircraft. First flown in 1955 and still in production, more Cessna 172s have been built than any other aircraft.

Measured by its longevity and popularity, the Cessna 172 is the most successful mass produced light aircraft in history. The first production models were delivered in 1956 and they are still in production. As of 2008, more than 43,000 had been built. The Skyhawk's main competitors have been the Beechcraft Musketeer and Grumman AA-5 series (neither in production), the Piper Cherokee and, more recently, the Diamond DA40.

The Cessna 172 started life as a tricycle landing gear variant of the taildragger Cessna 170, with a basic level of standard equipment. In January 1955 the company had flown an improved variant of the Cessna 170, a Continental O-300-A powered Cessna 170C with a larger elevator and more angular vertical tail. Although the variant was tested and certified, Cessna decided to modify it with a tricycle landing gear and the modified Cessna 170C flew again on 12 June 1955. To reduce the time and cost of certification the type was added on to the Cessna 170 type certificate as the Model 172. Later the 172 was given its own type certificate 3A12. The 172 became an overnight sales success and over 1,400 were built in 1956, its first full year of production.

Early 172s were similar in appearance to the 170, with the same straight aft fuselage and tall gear legs, although the 172 had a straight vertical tail while the 170 had a rounded fin and rudder. Later 172 versions incorporated revised landing gear and the sweptback tail which is still in use today. The final aesthetic development in the mid-1960s, was a lowered rear deck that allowed an aft window. Cessna advertised this added rear visibility as "Omni-Vision" . This airframe configuration has remained almost unchanged since then, except for updates in avionics and engines, including the Garmin G1000 glass cockpit in 2005. Production had been halted in the mid-1980s, but was resumed in 1996 with the 160 hp (120 kW) Cessna 172R Skyhawk and was supplemented in 1998 by the 180 hp (135 kW) Cessna 172S Skyhawk SP.

The Cessna 172 may be modified via a wide array of Supplemental Type Certificates, including increased engine power and higher gross weights. Available STC engine modifications increase power to 180 to 210 hp (134 to 157 kW), add constant speed propellers, or allow the use of automobile gasoline. Other modifications include additional fuel tank capacity in the wing tips, add baggage compartment tanks, add wheel pants to reduce drag, or enhance landing and takeoff performance and safety with a STOL kit.

On December 4, 1958 Robert Timm and John Cook took off from McCarran Airfield, Las Vegas, NV in N9172B. Sixty-four days, 22 hours, 19 minutes and 5 seconds later, they landed back at McCarran Airfield on February 4, 1959. The flight was part of a fund raising effort for the Damon Runyon Cancer Fund. Food and water were transferred by matching speeds with a chase car on a straight stretch of road in the desert, and hoisting the supplies aboard with a rope and bucket. Fuel was taken on by hoisting a hose from a fuel truck up to the aircraft, filling an auxiliary belly tank installed for the flight, pumping that fuel into the aircraft's regular tanks, and then filling the belly tank again. The drivers steered while a second person matched speeds with the aircraft with his foot on the vehicle's accelerator pedal.

Engine oil was added by means of a tube from the cabin that was fitted to pass through the firewall. Only the pilot's seat was installed. The remaining space was used for a pad on which the relief pilot slept. The right cabin door was replaced with an easy-opening, accordion-type door to allow supplies and fuel to be hoisted aboard. Early in the flight, the engine driven electric generator failed. A Champion wind driven generator (turned by a small propeller) was hoisted aboard, taped to the wing support strut, plugged into the cigarette lighter socket—and served as the aircraft's source of electricity for the rest of the flight. The pilots decided to end the marathon-flight because, with 1558 hours continuous running during the record-setting flight plus several hundred hours already on the engine beforehand (considerably in excess of its normal overhaul interval), the engine's power output had deteriorated to the point that they were barely able to climb away after refueling. The aircraft is on display in the passenger terminal at McCarran International Airport. Photos and details of the record flight can be seen in a small museum on the upper level of the baggage claim area.

Future models

172TD

On October 4, 2007 Cessna announced its plan to build a diesel-powered Cessna 172 model starting in mid-2008. The planned engine was to be a Thielert Centurion 2.0, liquid-cooled, two-litre displacement, dual overhead cam, four-cylinder, in-line, turbo-diesel with full authority digital engine control. The engine produces 155 hp (116 kW) and burns Jet-A fuel. The engines were to be installed at the Cessna Skyhawk factory in Independence, Kansas under an STC. The new model was designated the 172 Skyhawk TD, indicating "Turbo Diesel".

In early 2008 certification had been planned for the summer of 2008 and Cessna had forecast delivering about 125 TDs before the end of 2008. The TD was intended to sell for about USD$15,000 more than the top of the line "SP" Skyhawk and $35,000 more than the "R". Early orders for the TD were strong with most of the demand from flight schools and non-US operators. In April 2008 the 172TD's engine manufacturer, Thielert filed for insolvency under German law, throwing the future of the aircraft into doubt. On May 1, 2008 Cessna announced that they had cancelled all 2008 deliveries of the 172TD due to the insolvency of Thielert. The company stated: "At this point we have decided that we will not deliver 172TD aircraft during 2008, and we have informed our customers accordingly." Cessna has indicated that they still wish to produce a diesel 172 as market demand is strong for this aircraft with over 100 orders. Despite the issues at Thielert, Cessna indicated that they will proceed with the certification of the 172TD. The STC for the installation of the engine in the aircraft was completed in 2009, with Thielert Aircraft Engines GmbH the holder of the certificate. Cessna does not currently offer this model and it is not listed on the current type certificate.]

Electric-powered 172

In July 2010 Cessna announced it was developing an electrically powered 172 as a proof-of-concept in partnership with Bye Energy. In July 2011 Bye Energy, whose name had been changed to Beyond Aviation, announced that the prototype had commenced taxi tests on 22 July 2011 and that a first flight would follow soon.

Military operators

A variant of the 172, the T-41 Mescalero was used as a trainer with the United States Air Force and Army. In addition, the United States Border Patrol uses a fleet of 172s for aerial surveillance along the Mexican-American border.

The Irish Air Corps uses the Reims version for aerial surveillance and monitoring of cash, prisoner & explosive escorts in addition to army co-operation and pilot training roles. The type is popular and successful in service despite some accidents. Air Corps examples are painted dark green and carry the service roundels. Most are not fitted with the distinctive wheel spats.

In 1964, the US Air Force decided to use the off-the-shelf Cessna 172 as a preliminary flight screener for pilot candidates and ordered 237 T-41As from Cessna.

The T-41B was the US Army version, with a 210 hp (160 kW) Continental IO-360 and constant-speed propeller in place of the 145 hp (108 kW) Continental O-300 and 7654 fixed-pitch propeller used in the 172 and the T-41A.

In 1968, the US Air Force acquired 52 more powerful T-41Cs, which used 210 hp (160 kW) Continental IO-360 and a fixed pitch climb propeller, for use at the Air Force Academy (USAFA) in Colorado Springs.

In 1996, the aircraft were further upgraded to the T-41D, which included an upgrade in avionics and to a constant-speed propeller.

Beginning in 1993, the United States Air Force replaced much of the T-41 fleet with the Slingsby T-3A Firefly for the flight screening role, and for aerobatic training, which was outside the design capabilities of the T-41. The T-3A fleet was indefinitely grounded in 1997 and scrapped in 2006 following a series of fatal accidents at the United States Air Force Academy.

The Air Force now trains through a civilian contract with DOSS Aviation known as Initial Military Flight Screening which makes use of the Diamond DA20.

A number of USAF Academy T-41 were eventually distributed to various USAF Aero Clubs. Some of these aircraft developed structural cracks, forcing their grounding.

Three T-41s remain at the Air Force Academy in order to support certain academic classes as well as the USAFA Flying Team.

A number of air forces, including Saudi Arabia and Singapore, purchased various civilian models of the Cessna 172 for use in the military training, transport and liaison roles. While similar to the T-41, these aircraft were not T-41s and were powered by the standard 172 powerplants available in the model year purchased. These included the 145 hp (108 kW) Continental O-300 in pre-1968 aircraft and the 150 and 160 hp (120 kW) Lycoming O-320 in later 172s.