In the Scandinavian countries, that's what the Vikings believed that the Northern Lights were. In all actuality, it's the magnetosphere. But yes, traditionally, many things that have thought to have been dragons have been found to be just natural things.
In Sumerian folklore, there's a story about a terrible and fierce Firebird. What that Firebird actually probably was, was a meteor shower.
One of the most interesting though is this story:
During the march of the 300 Spartans to Persia, a sort of soldier's journal was collected whence they stopped to rest for a night. He wrote that when they awoke the next morning they looked from camp upward and saw two Suns in the sky. They took this to be a good omen of fortune.
What they actually saw, was the death of a G-Type Star like our Sun, going Supernova. Today, that is now the Crab Nebula:
It's a very, very rare occurrence that humans get to witness such an event. Most G-Type Stars live for Billions of years, and are so far away from us that we typically can't see such an event with the naked eye. It's actually kind of the only known and proven time that humans have seen such a thing within our recorded history.
The next time that will happen will be with the star Betelgeuse, one of the shoulders in the Orion constellation. Although we don't know specifically when that might happen, ETA is like an estimation of Tomorrow - 100,000 years, we do know, that if humans are around when it does happen, that for about 4 - 6 nights, the explosion will light up the night sky and outshine the Moon with multiple colors.