The Last Trumpet Call

Immediately after the tribulation of those days, the sun shall be darkened, and the moon shall not give its light; and the stars shall fall from heaven, and the powers of the heavens shall be shaken. 

And then shall appear the sign of the Son of Man in heaven, and then all the tribes of the earth shall mourn, and they shall see the Son of Man coming on the clouds of heaven with power and great glory. 

And He shall send His angels with a great sound of a trumpet, and they shall gather together His elect from the four winds, from one end of heaven to the other. 

...

Assuredly I say to you, this generation shall by no means pass away till all these things are fulfilled. 

Heaven and earth shall pass away, but My words shall by no means pass away. 

But concerning that day and hour no one knows, not even the angels of heaven, but My Father only. Mat. 24:29-36.

The Rapture of The Church - Maybe

The disciples had asked a loaded question what shall be the sign of Your coming, and of the end of the world?  In answer to that question, Christ has talked about Judea's fall and Jerusalem's complete destruction including their beloved temple.  

He continues His answer; of that day and hour no one knows, no, not the angels of Heaven, but only My Father. Mat. 24:36.  Christ said that He did not know the answer to that question, even the angels don't know that, but Christ could fill in some blanks.  

Immediately.  This word, used here, is a real problem for people who believe that Christ was speaking about the Rapture.  We know that the Rapture did not happen immediately after the fall of Jerusalem. 

the sun shall be darkened, and the moon shall not give its light;  The images used here are not to be taken literally. They are often employed by the sacred writers to denote “any great calamities.” As the darkening of the sun and moon, and the falling of the stars, would be an inexpressible calamity, so any great catastrophe - any overturning of kingdoms or cities, or dethroning of kings and princes is represented by the darkening of the sun and moon. Barnes.  So was Christ simply referring to political upheavals in Jerusalem?

After the sixth seal is opened in The Book of The Revelation John writes the sun became black as sackcloth of hair, and the whole moon became like blood. And the stars of heaven fell to the earth. Rev. 6:12-13.  Even if what Matthew wrote about the sun and moon refers only to Jerusalem's problems after the fall of Jerusalem John, writing in the future tense, wrote the same thing about the era in which the Rapture will happen.

Those Bible students who say that Matthew is not speaking about the Rapture have a problem with this phrase; then shall appear the sign of the Son of Man in heaven.  They say this does not mean that Christ is coming for the Church but the sign of the Son of Man refers to Christ's power and great glory as it is revealed in His Church from the Day of Pentecost till the Rapture.

The most feasible approach is to accept that Christ was making a double prophecy.  It seems to be the only way to make all His words fit into the picture.

The Rapture of the Church - Definitely

Throughout history Jews have been scattered worldwide.   Some Bible scholars say that all the tribes (races) (Strong G5443) of the earth means only the Jewish race.  In the next verse, Christ may have been speaking of the re-gathering of the Jewish people.  He said they shall gather together His elect from the four winds, from one end of heaven to the other.  This, of course, did not happen before Rome destroyed Jerusalem. Therefore it is feasible that Christ was speaking of a time just before the Rapture.

In The Revelation, John wrote the kings of the earth ... the rich and the mighty, and every slave and every free man ... said to the mountains and crags, Fall on us and hide us from the face of Him that sits on the throne, and from the wrath of the Lamb! Rev 6:15-16.  It seems ironic that Christ warned the Judeans to flee and hide in the caves for safety when the Roman army comes, and now, in this scene, when Christ comes with power and great glory people will again hide in caves to escape the wrath of the Lamb!

He shall send His angels with a great sound of a trumpet.  Those who believe this does not refer to the Rapture say His angels pertains to his messengers, the apostles, and their successors in the Christian ministry. Clarke.  It is correct to say that the word angels can be translated as messengers.

The words, With a great sound of a trumpet - Or, a loud-sounding trumpet - the earnest affectionate call of the Gospel of peace, life, and salvation. Clarke. I have an aversion to spiritualizing ideas in the Bible that can be taken more literally.

Concerning the Rapture St. Paul wrote Because the Lord Himself shall descend from heaven with a word of command, with the voice of an archangel, and with the trumpet of God. 1 Thes. 4:16.  In this setting, obviously, the sound of the trumpet does not refer to spreading the gospel of salvation.  It is much more akin to the trumpet call of judgment.

Saint John wrote, And the seventh angel sounded the trumpet: and there were great voices in heaven, saying: The kingdom of this world is become our Lord's and his Christ's, and he shall reign for ever and ever. 

this generation shall by no means pass away till all these things are fulfilled.

this generation:  that present age, or generation of men then living in it; and the sense is, that all the men of that age should not die, but some should live (till Christ's return). Gill.  When Gill uses the words "Christ's return" he is referring to the meaning he used before - Christ's power and great glory as it is revealed in His Church.  He is not relating it to Christ's return to earth or to the Rapture.

this generation: A generation is about 30 or 40 years. The destruction of Jerusalem took place about forty years after this was spoken. Barnes.  

this generation:  When Israel became a nation, again, in 1948, preachers told us that the word generation meant those people who were alive at that time and that they would not pass away before the Rapture of The Church took place.  Christ had warned us not to set dates for His return!

this generation: this race; i.e. the Jews shall not cease from being a distinct people, till all the counsels of God relative to them and the Gentiles be fulfilled. Clarke.  This is probably the right meaning for the word generation as it is used here.