Long-range, pressurized Lockheed Constellations and Douglas DC-6s joined KLM's fleet in the late 1940s; the Convair 240 short range pressurized twin engined airliner began European flights for the company in late 1948. During the immediate post-war period, the Dutch government expressed interest in gaining a majority stake in KLM, thus nationalizing it. Plesman allowed the Dutch government to acquire a minority stake in the airline. The expansion of the network continued in the 1950s with the addition of several destinations in western North America. KLM's fleet expanded with the addition of new versions of the Lockheed Constellation in 1953.

On 31 December 1953, the founder and president of KLM, Albert Plesman, died at the age of 64. He was succeeded as president by Fons Aler. The Netherlands government increased its ownership of the company to two-thirds, thus nationalizing it. The board of directors remained under the control of private shareholders. In July 1957, the airline introduced its Douglas DC-7C, the last KLM aircraft with piston engines, which opened the transpolar route from Amsterdam via Anchorage to Tokyo on 1 November 1958.

The four-engine turboprop Vickers Viscount 800 was introduced on European routes in 1957. Beginning in September 1959, KLM introduced the four-engine turboprop Lockheed L-188 Electra onto some of its European and Middle Eastern routes.

In March 1960, the airline introduced the first Douglas DC-8 jet into its fleet. The KLM logo was largely redesigned in 1961 by F.H.K. Henrion. The crown, formed by a line, four blue circles and a cross, was retained. By 1966, the stake of the Dutch government in KLM was reduced to a minority stake of 49.5%. In 1966, KLM introduced the Douglas DC-9 on European and Middle East routes.

The new terminal buildings at Amsterdam Airport Schiphol opened in April 1967, and in 1968 the stretched Douglas DC-8-63 entered service. With 244 seats, it was the largest airliner at the time. KLM was the first airline to put the higher-gross-weight Boeing 747-200B into service in February 1971, this began the airline's use of widebody jets.

In 1972, it purchased the first of several McDonnell Douglas DC-10 aircraft. In 1973, Sergio Orlandini was appointed to succeed Gerrit van der Wal as president of KLM. At the time, KLM, as well as other airlines, had to deal with overcapacity. Orlandini proposed to convert KLM 747s to "combis" that could carry a combination of passengers and freight in a mixed configuration. In November 1975, the first of these Boeing 747-200B Combi aircraft were added to the KLM fleet. The oil crisis of 1973, which caused difficult economic conditions, led KLM to seek government assistance in arranging debt refinancing. The airline issued additional shares of stock to the government in return for its money. In the late 1970s, the government's stake had again increased to a majority of 78%, re-nationalizing it. The company management remained under the control of private stakeholders.

In 1983, it reached an agreement with Boeing to convert ten of its Boeing 747-200 aircraft to stretched-upper-deck configuration. The converted aircraft were called Boeing 747-200SUD or 747-300, which the airline operated in addition to three newly build Boeing 747-300s. In 1983, KLM took delivery of the first of ten Airbus A310 passenger jets. Sergio Orlandini retired in 1987 and was succeeded as president of KLM by Jan de Soet.

In 1986 the Dutch government's shareholding in KLM was reduced to 54.8 percent. It also replaced its short haul fleet with the arrival of Boeing 737-300 aircraft and later B737-400 in 1989. For long haul routes, the Boeing 747-400 was introduced in June 1989.

With the liberalization of the European market, KLM started developing its hub at Amsterdam Airport Schiphol by feeding its network with traffic from affiliated airlines. In December 1991, KLM was the first European airline to introduce a frequent flyer loyalty program, which was called Flying Dutchman.

KLM City Hopper, the regional franchise of KLM, was established on 1 April 1991 and started operations the same year. It was formed from the merger of NLM CityHopper and Netherlines. KLM Cityhopper had Europe's largest fleet composition of all Fokker-built aircraft: the Fokker 50, 70 and 100.

In January 1993, the United States Department of Transportation granted KLM and Northwest Airlines anti-trust immunity, which allowed them to intensify their partnership. The same year KLM also received its MD-11 for long haul operations. KLM introduced the Boeing 767-300ER in July 1995.

In January 1996, KLM acquired a 26% share in Kenya Airways, the flag-carrier airline of Kenya. In August 1998, KLM repurchased all regular shares from the Dutch government to make KLM a private company. In 1999 the first next generation Boeing 737-800 arrived into the fleet for European and short haul routes.

KLM renewed its intercontinental fleets by replacing the Boeing 767s, Boeing 747-300s, and eventually the McDonnell Douglas MD-11, with Boeing 777- 200ERs and Airbus A330-200s in 2003. The MD-11s remained in service until October 2014.

KLM saw the introduction of the Boeing 737-900 in August 2001, at the time the largest member of Boeing’s Next Generation 737 family. The aircraft was delivered on 29 August 2001, becoming one of the earliest -900 variants to enter commercial service in Europe. The Boeing 737-900 offered increased capacity compared to the airline’s existing 737-700 and 737-800 fleet.

On 30 September 2003, Air France and KLM agreed to a merger plan in which Air France and KLM would become subsidiaries of a holding company called Air France– KLM. Both airlines would retain their own brands, and both Charles de Gaulle Airport in Paris and Amsterdam Airport Schiphol would become key hubs. In September 2004, the merger was completed by creation of the Air France–KLM holding company. KLM's long standing joint venture with Northwest Airlines, which merged with Delta Air Lines in 2008, was unaffected by the merger with Air France. As both airlines KLM and Northwest joined the SkyTeam alliance in September 2004.

KLM's first Boeing 777-200R landed at Schiphol in October 2003. The aircraft provided services to Cape Town, Nairobi, and New York. Two years later the first Airbus A330-200 was introduced on 25 August 2005.

In March 2007, KLM started to use the Amadeus reservation system, along with partner Kenya Airways. In 2008 the airline announced its fleet renewal programme for its regional subsidiary KLM City Hopper, starting with an order of up to 17 Embraer 190-100 aircraft to replace its ageing and inefficient Fokker 50 aircraft and older Fokker 100 jets. The first Embraer jets E190 arrived one year later in 2009. In 2008 the airline also received its first Boeing 777-300ER for long haul operations.

Beginning in September 2010, KLM integrated the passenger division of Martinair into KLM, transferring all personnel and routes. By November 2011, Martinair consisted of only the cargo and maintenance division. On 19 June 2012, KLM made the first transatlantic flight fuelled partly by sustainable biofuels to Rio de Janeiro. This was the longest distance any aircraft had flown on biofuels at the time.

On the 14 November 2015, KLM welcomed its first Boeing 787-9 Dreamliner.