Fighter aircraft deploy flares to distract surface to air missiles which are guided by heath. There are various videos on YouTube which show aircraft deploying flares.
Those hot flares could have caused the fire at the alleged launch location south of Snizhne.
The Interpreter quotes an eyewitness named Marina who lives in Pervomaika [Pervomaiskoye]
Marina: Before that [the crash of the Boeing-PN), that day there were four people: Aunt Nina, Aunt Lyuba and my friend, Godmother Lyuda. We were sitting on the bench and talking. The drones were flying. Then we went our ways. And then Aunt Nina comes running out and starts calling us, and covered her face with her kerchief. And the missiles flew at us here, like fireworks, missiles, but they were white. There were a lot of them, they opened up, and then they hung in the sky, and she [Aunt Nina], thought that they were phosphorous bombs. Before that they scared us, that they had been in Makeyevka, that there would be burns later. [Aunt Nina] shouted – “phosphorous bombs!” And here Sergei came along [her husband, who served in the DNR–PK] and says “Aunt Nina, that can’t be, that’s the defense.”
Kanygin: Thermal [defense from an MRLS]?
Marina: Yes. And the sky was whitish, like fog.
Kanygin: Your neighbor told me that this plane which ejected thermal defense was then shot down.
Marina: Well, of course! It was shot down over Dmitrovskaya.