Military Flares
It’s a bird! It’s a plane! No, it’s on fire! Seriously, what is that thing? We’ve never heard of birds spontaneously combusting midflight, and we try not to think of anything bad happening to aircrafts. The OP was helpful enough to provide further info about this image. Apparently, they shot this image nearby a military base.
That’s all the info online users needed to determine what this strange formation in the sky was. It was the result of a flare gun going off, which was probably done to signal that they were going to run a kind of military drill of sorts.