This question appears to assume the popular mythology that Satan is a fallen angel. In fact, the Bible contains no such teaching. (See “Is Satan a fallen angel?”)
Bible imagery – falling from heaven:
In the Bible, “falling from heaven” is figurative of losing authority. To cite three examples, Isaiah 14:12 describes the king of Babylon as “fallen from heaven” (see also Jeremiah 51:53), the king of Tyre was “thrown to the earth” in Ezekiel 28:17, and Israel’s splendour was hurled “from heaven to earth” in Lamentations 2:1. A fourth example is again from Jesus himself:
And you, Capernaum, will you be lifted to the heavens? No, you will go down to Hades. For if the miracles that were performed in you had been performed in Sodom, it would have remained to this day. (Matthew 11:23)
Clearly Capernaum wasn’t physically going up or down anywhere, this is allegorical and apocalyptic imagery.
There are two passages that talk about Satan “falling”:
He [Jesus] replied, “I saw Satan fall like lightning from heaven.” (Luke 10:18)
Here, Jesus is responding to his disciples reporting how they had been able to cure people of illnesses.
While the disciples were amazed at the power they had over disease, Jesus was thinking of his ultimate triumph over sinful human nature. Elsewhere Jesus emphasised the link between sin and illness (e.g., Matthew 9:5), and equated Satan with temptation to sin (Matthew 4:10). In other words, he is saying “You’ve seen illness cured, but wait until you see sin, the ultimate sickness, destroyed!”. Thus, the verse is parallel to Hebrews 2:14:
Since the children have flesh and blood, he [Jesus] too shared in their humanity so that by his death he might destroy him who holds the power of death—that is, the devil— (Hebrews 2:14)
Additional material on Luke 10:18 can be found in Ron Abel’s Wrested Scriptures, here.
The second verse that mentions Satan falling is from Revelation.
The great dragon was hurled down—that ancient serpent called the devil, or Satan, who leads the whole world astray. He was hurled to the earth, and his angels with him. (Revelation 12:9)
Revelation is highly symbolic, and we have to be careful in identifying the symbols used. The dragon called Satan represents something, as do all the other features of this parable-vision such as the seven heads with crowns on, the ten horns, the tail catching hold of the stars, the angels and even heaven—all of these represent something. It makes no sense to try to understand this vision literally. Who ever heard of a fallen angel with seven heads and ten horns!
Also, look at the context. The very next verse (Revelation 12:10) says that as a consequence of the dragon’s downfall, people will rejoice because God’s kingdom has come. This shows that the event described in this vision must be still future, since we know that God’s kingdom has not yet come.
Most likely, the dragon being hurled down represents the defeat of the power of sin and the end of human kingdoms when Jesus returns to establish his kingdom. There are clear parallels with the fourth beast of Daniel 7 which also had ten horns. It represented a human kingdom that would be overthrown when Jesus returns (Daniel 7:19-23).
If the dragon falling leads to the coming of the kingdom, what does verse 12 mean when it talks about the heavens rejoicing, while the earth and sea have woes. Surely the kingdom of God coming from heaven to earth would be a time of rejoicing, not of woe? Then after the woman has fled into the desert verse 17 refers to the dragon going off to make war on the rest of the woman’s offspring, those who keep the commandments of God and hold to the testimony of Jesus. Surely such persecution shouldn’t be happening to the saints after the kingdom of God has come?
Similarly, Revelation 13 seems to follow directly on from Revelation 12, and it refers to another beast which the dragon gives its authority to, and this other beast is also blaspheming God and making war on the saints and conquering them, all of which seem to me to point to a time before the coming of the kingdom.