 Another pro-LNA MiG-21 fighter jet was shot down by Islamists MANPADS over the town of Derna on 31 July 2017 during its bombing raid on Islamist positions in the town of Derna, both of its pilots ejected safely and were then captured by the Islamists.Also, on 18 May, pro-GNA militias launched a successful surprise offensive on the pro-LNA Brak al-Shati air force base in the area of Fezzan in southern Libya, killing over 140 pro-LNA soldiers and civilians (of which 40 were executed after being captured), heavily damaging the Brak al-Shati air force base, and also destroyed one inoperable pro-LNA L-39ZO Albatros fighter jet on the ground.Pro-LNA Libyan air force lost at least six to eight helicopters — Mi-8, Mi-14, Mi-24/Mi-35 and Mi-17—between 2014 and 2017, most of them crashed due to technical malfunctions, but one pro-LNA Mi-35 combat attack helicopter was shot down at Ras Lanouf and another pro-LNA Mi-35 combat attack helicopter was abandoned by the pro-LNA forces at Ras Lanouf air force base during a pro-GNA militant surprise offensive in March 2017, the helicopter was subsequently destroyed on the ground by the pro-GNA militants in order to prevent its recapture by the pro-LNA forces.