Do we go "up" or "down" after being caught up in 1 Thessalonians 4:17?
Answer: No saved soul will ever return to earth. We will step out of finite time into Christ's eternal Presence: He will never set foot on planet earth again.
With respect, I am responding to this from an amillennial perspective with the recognition that much of what we read in several texts arises from biblical symbolism. Apparently, that may be unpalatable to some which seems a real shame. I wrote a parallel response to a question of this form elsewhere.
The OP’s query provokes some amazing truths. Suppose we consider the words of Peter for a moment:
2 Peter 3:3-4a: “Know this [that] in the last days mockers will come with their mocking, following after their own lusts, 4and saying, “Where is the promise of His coming?’” (emphasis added).
Although I strenuously disagree with such mockers (for reasons that I will explore), just how do these skeptics not have a point? Christ promised to His disciples thousands of years ago that He would return to them. Did He?
Recall what is said in dozens of passages, starting with the one from the OP:
1 Thessalonians 4:17: “Then we who are alive and remain will be caught up together with them in the clouds to meet the Lord in the air, and so we shall always be with the Lord.”
1 Thessalonians 5:2: “For you yourselves know perfectly that the day of the Lord so comes as a thief in the night.”
Luke 12:39: “But know this, that if the master of the house had known what hour the thief would come, he would have watched and not allowed his house to be broken into.”
Everyone who is saved will meet the Lord "up" in the air symbolically, because heaven is "up" — or "beyond" this material world of space and time. And, this will occur in the same moment from our own individual perspectives, exactly as we’re told, which I’ll describe.
The Lord’s Return represents the eventuality of all the faithful, presumably including Adam and Eve, dating back to the very beginning. Preferential treatment seems especially unlikely; one way or another, everyone is a descendant of our great ancestor, Adam, and “[All] have sinned and fall short of the glory of God” (Romans 3:23). Moreover, God does not play favorites; it would be egregiously unfair that a single generation, say, in the year 3,000, would be the only one to witness arguably the greatest event in the history of the world (cf. John 14:2-3).
I've included a figure below intended to depict how every faithful soul is immediately ushered into the Presence of the Lord where "up" or "down" is of no significance. As we do so, we will be clothed with immortality; the encounter coincides with Christ's Return: “We will be caught up together [with those who have already departed] to meet Him (and them) in the air.”
As far as we on Earth are concerned, time continues to forge onward while we remain. However, it must be emphasized that, for the saints who have departed this world, there is no longer any passage of time — an irresistible consequence of timelessness. Again, although these conditions represent a future event to us, no saved soul will exist as a disembodied spirit without form. One might conceptualize the proposed circumstances this way: our individual death and Christ’s return are essentially synonymous as far as we experience them.
An analogy might suffice: Suppose we see our close relatives off on a flight to another city. As soon as they arrive at their destination, they are thrilled to discover that we too were on the plane with them. The reason that no one is yet in heaven (Acts 2:34, etc.) is that we are not yet there either. But as soon as we arrive, all of the faithful dating to the end of physical time will be there along with us!
How timelessness in God's realm works at all is another matter entirely. Mark 13:32 states that "[No] one knows about that day or hour" when the event will occur, despite the fiction by many modern-day “prophets” who adamantly claim otherwise. If these considerations are correct — all based entirely on Scripture — "when" Christ returns is irrelevant since all the faithful will experience the event indistinguishably from one another.
To date, I've discovered over 150 passages (I understand there are over 300) detailing the Lord's Return, the central theme of the New Testament. (Mercifully, I have excluded them in this discussion.)
What is crucial to understand is the great distinction between finite time in this world, and the timelessness of eternity. Most are probably aware of the phrase used by the New Testament to describe Christ's Return "as a thief in the night" (Mark 13:32, Luke 12:39, 2 Peter 3:10, 1 Thessalonians 5:2, Revelation 16:15).
Suppose we think very carefully about that for a moment. What event in everyone's life comes to them suddenly without warning? Think of how you might encounter some fatal accident. Or consider someone who has been bedridden for months, each day expecting everything to be just as it was before without incident. That is until we each experience our last day (John 6:40, 44) — the end of our physical life on earth forever.
This is the day we step "up" or "out" or "beyond" this world into eternity, a realm where time ceases to elapse (certainly, as we now recognize it). Nowhere does the Bible teach that Christ will ever set foot on Earth again; no, we will step into His Presence in the clouds just as Scripture clearly tells us (Acts 1:11, 1 Thess. 4:17, etc.). Some will claim that He will stand on the Mount of Olives, without realizing the symbolism.
What they seem to overlook is that Christ did literally stand on the Mount of Olives throughout His ministry. He had been a guest of Mary, Martha, Lazarus (in Bethany, on Mount Olivet). His ascension was from the Mount of Olives (cf. Luke 24:50-51, Acts 1:12). And, He suffered in the Garden of Gethsemane as His sweat "became like great drops of blood" — yes, on the Mount of Olives! We should recognize that this is where Christ "stood" or "placed his feet" on the Mount. Christ most definitely planted "His feet in that day upon the Mount of Olives" — as metaphorically described (Zech. 14:4). (This is fantastic symbolism!)]
Note how we might envision 1 Thessalonians 4:17, as we ascend "up into the clouds" as I've illustrated. The Figure is meant to depict the emergence of the human spirit into one of two destinations: Paradise above or Hades below. Note that Earth history proceeds horizontally in increments of approximately 200 years. It seems that those in Hades must continue to experience the passage of time in agony (Lk. 16:19+) — unlike the saints who cross the threshold of finite time into eternity.
This is the way I believe we might understand our circumstances outside of finite time: the saints enter the eternal realm at the same timeless instant from each of our perspectives. I do not believe this is true for those who are lost and are currently suffering the torment of fire (Luke 16:19+, "spirits [now] in prison": 1 Pet. 3:19, 2 Pet. 2:4).
Note that Lazarus was in "Abraham's Bosom." Where is that, exactly? After all, Noah died long before Abraham was born. I submit that Abraham's Bosom is meant to characterize paradise, just as depicted.
It makes no difference at all whether this is "up," "down," or otherwise as stated in 1 Thessalonians 4:17.