This is good ol’ fashion comparing Scripture with Scripture.
Notice all five passages link between (1) Christ appearing in the sky and (2) the gathering of God’s people.
1 Thessalonians 4:15–17
“For we tell you this by the word of the Lord, that we who are alive, who are left until the coming [parousia] of the Lord, will surely not go ahead of those who have fallen asleep. For the Lord himself will come down from heaven with a shout of command, with the voice of the archangel, and with the trumpet of God, and the dead in Christ will rise first. Then we who are alive, who are left, will be suddenly caught up together with them in the clouds to meet the Lord in the air. And so we will always be with the Lord” (cf. 2 Thess 1:4–10!).
“For just like the lightning comes from the east and flashes to the west, so the coming [parousia] of the Son of Man will be. Wherever the corpse is, there the vultures will gather. Immediately after the suffering of those days, the sun will be darkened, and the moon will not give its light; the stars will fall from heaven, and the powers of heaven will be shaken. Then the sign of the Son of Man will appear in heaven, and all the tribes of the earth will mourn. They will see the Son of Man arriving on the clouds of heaven with power and great glory. And he will send his angels with a loud trumpet blast, and they will gather his elect from the four winds, from one end of heaven to the other.”
“Then they will see the Son of Man arriving in a cloud with power and great glory. But when these things begin to happen, stand up and raise your heads, because your redemption is drawing near.”
“Then I looked, and a white cloud appeared, and seated on the cloud was one like a son of man! He had a golden crown on his head and a sharp sickle in his hand. Then another angel came out of the temple, shouting in a loud voice to the one seated on the cloud, ‘Use your sickle and start to reap, because the time to reap has come, since the earth’s harvest is ripe!‘ So the one seated on the cloud swung his sickle over the earth, and the earth was reaped” (cf. Rev 1:7).
Revelation 6:14, 16; 7:9, 13–14
“The sky was split apart like a scroll being rolled up. . . . They said to the mountains and to the rocks, ‘Fall on us and hide us from the face of the one who is seated on the throne and from the wrath of the Lamb,’ . . . . “After these things I looked, and here was an enormous crowd that no one could count, made up of persons from every nation, tribe, people, and language, standing before the throne and before the Lamb dressed in long white robes, and with palm branches in their hands. . . . . Then one of the elders asked me, ‘These dressed in long white robes—who are they and where have they come from?’ So I said to him, ‘My lord, you know the answer.’ Then he said to me, ‘These are the ones who have come out of the great tribulation. They have washed their robes and made them white in the blood of the Lamb!’
Someone may object that I am taking these passages out of their context. Actually, if one examines each context they will learn that before each passage there is mention of eschatological persecution for God’s people, and after each passage there is mention of the eschatological wrath of God. So the cohesive thread of continuity is much greater than what is mentioned here! For further study, see my Antichrist Before the Day of the Lord.