Państwowe Zakłady Lotnicze (national aviation establishment) was set up as Poland’s main aircraft design and production organization 1 January 1928, having previously been CZL (central aviation establishment) and originally in 1919 CWL (central Warsaw aviation establishment), handling repair and maintenance only. Para-military government of 1926 urged better defences, and PZL concentrated on fighters with brilliant team of young graduates led by Zygmunt Puławski. First, classic design, P.1 fighter introduced "Puławski wing" with inner section tapered in chord and thickness and sloped sharply down to join top of fuselage; led to more than 760 fighters of P.7, 11 and 24 basic types, majority for Romania, Turkey and Greece. Other types: L.2 STOL observation, L.3 bomber, L.4 and 27 trimotor airliners, PZL.5 2-seat biplane, P.19 3-seat tourer, P.23 and 43 Karaś bomber/recon, P.26 fast 3-seater and, not least, P.37 Łoś heavy bomber, outstanding aircraft of which 70 delivered but only 36 combat-ready on 1 September 1939. Increased demand led to original Warsaw-Okęcie factory being augmented by much larger factory at Mielec 1938. During Second World War and the five-year German occupation, all Polish aviation industry was taken over by German firms, and as a result, almost completely destroyed. By the end of the war, all factories were either ruined or robbed of tooling. Despite it, from 1944 there were carried out efforts to design new aircraft, in primitive conditions (first of all, in the LWD). No engines nor suitable production facilities were available at first. From the late 1940s the name PZL ceased to be used, and new factories were named WSK (Wytwórnia Sprzętu Komunikacyjnego - Transport Equipment Manufacturing Plant); see WSK-Mielec and WSK-Świdnik. Under the Soviet-influenced, centrally planned economy, all indigenous projects were abandoned, in a favour of manufacturing Soviet-licensed aircraft. No own designs were produced for a decade, and only in late 1950s did the PZL brand return to designing new aircraft. The ZPLiS PZL - Zjednoczenie Przemysłu Lotniczego i Silnikowego PZL - PZL Aircraft and Engine Industry Union, which grouped all state-owned aerospace industry factories, was created in following years, but it only enjoyed some economic autonomy from 1973 onwards. It consisted of 19 factories, a research institute, and the Pezetel Foreign Trade Center - CHZ Pezetel, which represented all the Polish aerospace industry abroad (Pezetel being the pronunciation of an abbreviation PZL in Polish). Consequently, in the 1970s some WSK factories also introduced the PZL abbreviation to their names. After the fall of communism in Poland in 1989, all manufacturers became separate companies, initially state-owned, still sharing the PZL name. See also PZL Mielec, PZL-Świdnik and PZL Warszawa-Okęcie.