In 1938 LOT changed its name, in accordance with the Polish spelling reform of that year from Polskie Linje Lotnicze 'LOT' to Polskie Linie Lotnicze 'LOT'. There were plans to open services among others to London and Moscow and even transatlantic service in 1940. Services were suspended after an outbreak of the Second World War on 1 September 1939 and during following German occupation; most of LOT's aircraft were evacuated to Romania, two to Baltic states, and three L-14H to Great Britain. Thirteen airliners, that got to Romania, were next seized by Romanian government.

After a liberation of Poland, from August 1944 until December 1945 the Polish Air Force maintained basic transport in the country. On 10 March 1945 the Polish government recreated the LOT airline, as a state-owned enterprise .

In 1946, seven years after the service was suspended, the airline restarted its operations after receiving ten Soviet-built ex-Air Force Lisunov Li-2Ts, then further passenger Li-2Ps and nine Douglas C-47s. Both domestic and international services restarted that year, first to Berlin, Paris, Stockholm and Prague.

In 1947 it added routes to Bucharest, Budapest, Belgrade and Copenhagen. Five modern, although troublesome SE.161 Languedoc joined the fleet for a short period in 1947–1948, followed by five Ilyushin Il-12B in 1949; 13-20 Ilyushin Il-14s then followed in 1955–1957.

After the end of Stalinism in Poland, few Western aircraft would be acquired; five Convair 240s in 1957 and three Vickers Viscounts in 1962 proved to be the last until the 1990s. After that, the composition of the airline's fleet shifted exclusively to Soviet-produced aircraft, like the Tupolev Tu-134. Only in 1955 LOT inaugurated services to Moscow, being the centre of the Marxist–Leninist world, and to Vienna. Services to London and Zürich were not re-established until 1958, and to Rome until 1960.

Nine Ilyushin Il-18 turboprop airliners were introduced in June 1961, leading to the establishment of routes to Africa and Middle East, and in 1963 LOT expanded its routes to serve Cairo. In the 1970s flights to Baghdad, Beirut, Benghazi, Damascus and Tunis were started. The Antonov An-24 was delivered from April 1966, followed by the first jet airliners Tupolev Tu-134 in November 1968 which were operated on European routes. The Ilyushin Il-62 long range jet airliner inaugurate the first transatlantic routes in the history of Polish air transport to Toronto in 1972 as a charter flight and a regular flight to New York City in 1973. LOT began service on its first Far East destination – Bangkok via Dubai and Bombay in 1977.

In 1977, the airline's introduced a revised livery (despite occasional changes, notably in corporate typography) with the large 'LOT' inscription in blue on the front fuselage, and a blue tail plane was introduced, with the original 1929 designed logo, despite many changes in livery, it was kept through the years, and to this day remains the same. In the Autumn of 1981, commercial air traffic in Poland neared collapse in the wake of the communist government's crackdown on dissenters in the country after the rise of the banned 'trade union' dissident Solidarity movement. Charter flights to New York and Chicago resumed only in 1984, and eventually regular flight connections were restored on 28 April 1985. Tupolev Tu-154 mid-range airliners were acquired, after the withdrawal of Il-18 and Tu-134 aircraft from LOT's fleet in the 1980s, and were deployed successively on most European and Middle East routes. In 1986 transatlantic charter flights also reached Detroit and Los Angeles.

After the fall of the communist system in Poland in 1989 the fleet shifted back to Western aircraft, beginning with acquisitions of the Boeing 767-200 in April 1989, followed by Boeing 767-300 in March 1990, ATR 72 in August 1991, Boeing 737-500 in December 1992 and finally the Boeing 737-400 in April 1993. LOT was among the first Central European countries to operate American aircraft when the Boeing 767 was introduced; the 767s were used to operate LOT's longestever connection to Singapore.

In 1990 ATR 72 aircraft were acquired for use on LOT's expanded route network, which began to include new international destinations such as Kiev, Lviv, Minsk and Vilnius. Soon thereafter, in 1993, LOT began to expand its Western-European operations, inaugurating, in quick succession, flights to Oslo, Frankfurt and Düsseldorf, operations at Poland's other regional airports outside Warsaw were also duly expanded around this time.

By December 1992 the airline became a joint stock company, as a transitional step towards partial privatisation, which was effected in late 1999. After years of planning, in 1997 LOT set up a sister airline, EuroLOT, which, essentially operating as its parent airline's regional subsidiary, took over domestic flights. The airline was developed with the hope that it would increase transit passenger-flow through Warsaw's Chopin Airport, whilst at the same time providing capacity on routes with smaller load factors and play a part in developing LOT's reputation as the largest transit airline in Central and Eastern Europe. By 1999 LOT had purchased a number of small Embraer 145 regional jets in order to expand its short-haul fleet.

Expansion of LOT's route network continued in the early 2000s and the potential of the airline's hub at Warsaw Chopin Airport to become a major transit airport was realised with more and more success. In 2000 LOT took delivery of its largest ever order of 11 aircraft. On 26 October 2003, LOT, became the 14th member of the Star Alliance. By 2006 a new base of operations, with the reconstruction of Warsaw Chopin Airport, had opened, thus allowing LOT's full transit airline potential to be developed for the first time ever.

In 2008 LOT opened a new flight to Beijing, however this lasted just a month, as LOT did not have permission for flights over Siberia from the Russian government, which was making the services too long and thus unprofitable. LOT started new services to Yerevan, Armenia, Beirut, Lebanon and resumed Tallinn, Estonia, Kaliningrad, Russia, Gothenburg, Sweden and Bratislava, Slovakia with its newly acquired Embraer aircraft in summer 2010, and in October of the same year LOT resumed service to Asia, with three weekly flights on the Warsaw-Hanoi route. In addition to this, new services to Tbilisi, Damascus and Cairo were inaugurated.

In 2010 LOT cancelled flights, after 14 years of operation, between Kraków and the US destinations of Chicago and New York, citing profitability concerns and lack of demand.

On 31 May 2010, CEO of LOT stated that the airline will be replacing its fleet to meet a goal of one-third new by 2011. Replacement already started with Embraer E-Jets 175/170. For domestic expanded operations, LOT purchased Dash 8-Q400 over ATR 72-600 aircraft.

On 5 February 2011, new routes to Tokyo and Beijing were launched. This was now feasible since the finalizing of an agreement on Siberian overflight permits for LOT by the Polish and Russian governments in November 2011. On the 24th June 2011, LOT presents the world's most modern passenger airplane, Boeing 787 Dreamliner, joining the fleet. LOT took delivery of a total of six Boeing 787 Dreamliners, with the remaining two aircraft expected to join the fleet by 2017.

Although delayed from the original plans, LOT began flights to Tokyo Narita Airport in Japan on 13 January 2016, with flights three times per week. In 2010/11 LOT also announced in line with its new policy, LOT introduced, for the first time, a premium economy on all Boeing 787 aircraft. Additionally lie-flat seats are available in business class and all of the airline's new long-haul aircraft have been fitted with Thales personal entertainment systems.

In June 2012 LOT announced all services to New York would be centralized to JFK Terminal 1 from October 2012. During 2012, LOT said goodbye to the last Boeing 767 in the fleet.

Amidst a restructuring plan which saw the airline return to profitability for the first time in seven years, a 22 June 2015 press conference revealed details pertaining to the airlines future prospects. These include reinstating routes renounced as part of EU sanctions imposed following Polish government aid granted to ensure the airline's survival, as well as new long haul routes to Asia and North America. As well, the same year, on 6 February 2015, it was announced that EuroLot would be liquidated due to financial problems and end operations on 31 March 2015. LOT Polish Airlines assumed some of Eurolot's routes, re-leasing former Eurolot aircraft.

As part of the airlines future fleet expansion, Air Lease Corporation confirmed on October 13, 2016 the placement of 6 Boeing 737 MAX 8 aircraft with LOT, and options to lease 5 further aircraft of the same type. Long haul plans saw the addition of further Boeing 787 aircraft, increasing the total to 16 in the coming years.