Syrian opposition factions announced on Tuesday that they had downed a regime fighter jet in the eastern Hama countryside.
The jet was taking part in military operations in the area, which had witnessed an unprecedented escalation that left 20 people dead.
The Free Idlib Army said the L-39 jet was shot down by anti-aircraft weapons.
Two pilots were on board the plane. The Syrian Observatory for Human Rights said that one was killed, while the fate of the other was not revealed.
It said that they initially made it out of the crash alive and tried to flee to a safe area until they could be rescued by Russian jets that are allied with the regime.
The regime intensified its bombardment of the region once it heard about the crash. A helicopter was dispatched in an attempt to find the pilots before they were captured or killed.
The opposition factions however managed to find them before they could be rescued.
In the southern and eastern Idlib countryside, the Observatory said that 20 people have been killed in regime bombardment that has been ongoing since Monday.
It also reported on fierce battles that had erupted once again between regime forces and opposition factions.
The fighting was focused on the outskirts of al-Mshayrfa, al-Katiba, Tal al-Aswad and the villages of Ras al-Ain and Qobayat Um al-Huda.
The Observatory said that the regime made advances in the region and it is trying to reinforce its positions in al-Katiba and Tal al-Aswad.