Aero L-39 Albatros L-39M1

The L-39M1 is the Ukrainian designation for the first stage of the upgrade of the L-39C trainer inherited from the Soviet Union. It is not a new-build aircraft but a conversion of existing airframes: each aircraft goes through a general overhaul at the Odesa plant — Odesaviaremservis in English-language sources, the State Enterprise "Odesa Aviation Plant" (DP "OAZ") of the Ukroboronprom concern in official releases — and leaves with an improved engine and new recording and navigation equipment. It should not be confused with the L-39M, the much deeper second stage of the same programme, which adds an on-board training suite simulating the MiG-29 weapon-aiming system, nor with the Slovak L-39CM and L-39ZAM upgrades.

The heart of the programme is the engine. In 2002 an upgraded version of the AI-25TL turbofan was developed for the L-39, with an additional maximum combat rating giving increased thrust and better acceleration at low altitude; it was named AI-25TLSh, and that same year it underwent flight testing by the Ukrainian Ministry of Defence. The Progress design bureau (Ivchenko-Progress) put it into series production in 2008. According to Russian and Ukrainian sources, the change raises thrust from 1,720 to 1,850 kgf (from about 16.9 to about 18.1 kN) and halves the engine's acceleration time; the technical note on the conversion puts the improvement in dynamic parameters at 10% and stresses its positive effect on flight and take-off and landing performance. Ivchenko-Progress also markets the AI-25TLSh as an upgrade for other L-39 and JL-8 operators, arguing that it extends the aircraft's service life and improves performance.

The L-39M1 was developed between 2002 and 2009 and was officially adopted by the Ukrainian Air Force by order No. 347 of the Minister of Defence dated 8 July 2009. Several Ukrainian defence companies took part in the programme: the Odesa plant, the Arsenal design bureau, the Progress engine design bureau, Orizon-Navigatsiya and Elektronprylad. Besides the engine change, the conversion improves the powerplant control system and installs an SN-3307 GPS satellite navigation receiver from Orizon-Navigatsiya and a BUR-4-1 crash-survivable flight data recorder with additional sensors from Elektronprylad (the 2020 releases already cite the BUR-4-1-07 version). The aim was to increase the information recorded on board and to create an automated system for processing flight data, improving the quality of training. The recorder work had precedents: from January 2005 the Chuhuiv aircraft repair plant replaced the old SARPP-12 recorder with the BUR-4-1 on ten L-39s for foreign customers, and in 2007 it did the same on six L-39s of Azerbaijan. After conversion the L-39M1 has a mass of 3,500 kg, a maximum speed of 785 km/h and a range of 980 km.

English-language Wikipedia places the first converted aircraft in 2009 and mentions a plan to upgrade a further seven L-39Cs; another source puts the plan at thirteen aircraft. The real pace was slow: the first two aircraft reached the Air Force in 2010, two more in December 2011 and two more on 26 June 2012, so six were in service when, at the end of 2013, work began on a seventh. In March 2014 three L-39M1s of the 204th Tactical Aviation Brigade, based at Belbek, were lost after Russia's annexation of Crimea. According to the Ukrainian Ministry of Defence White Book, no conversions were carried out in 2014, and in 2015 work continued but no aircraft was delivered.

Deliveries resumed in 2016, when the Odesa plant repaired and handed over two L-39M1s together with the first L-39M, and another L-39M1 followed in 2017. At the beginning of September 2017 four L-39M1s (tail numbers 101, 102, 103 and 107) were serving with the 40th Tactical Aviation Brigade at Vasylkiv airfield. The plant delivered another L-39M1 on 26 September 2018 and one more on 24 October 2018. For 2020 the state order covered the repair and upgrade of only two aircraft: the first was delivered on 23 November 2020, and the second, delayed by problems with equipment deliveries from subcontractors, made its test flight on 22 December and was handed over without remarks at the end of that month. In 2021 Air Force Command ordered, in several tenders, the repair of seven AI-25TLSh engines for its L-39s.

The L-39M1s were the aircraft on which Ukrainian fast-jet pilots were still training when Russia launched its full-scale invasion in 2022. On 25 August 2023 two Ukrainian Air Force L-39M1s collided in mid-air during dogfight training near Sinhury, in Zhytomyr Oblast, killing Majors Andrii Pilshchykov — known by his callsign "Juice" — Viacheslav Minka and Serhii Prokazin. The sources give no final total of L-39M1 conversions.