We've all seen victory homecoming parades, typically for a sports team - a great crowd goes out to line the streets, cheer and welcome. The sports team will doubtless end up at a banquet - in ancient Middle Eastern culture the arrival of a king or dignitary would see people venture out of their city to welcome the person, and then follow the cavalcade back in and share in the celebrations. For us it would be like lining the A10 out as far as Stretham, and then following back in to the centre of Ely!
This is the kind of scene Paul envisages in v16 and 17 - not of Caesar but of Jesus, the King of Kings, coming to bring his rule with proper justice and righteousness. Such rule finally brought would put an end to all wrong, all that spoils or breaks. The clouds and air of these verses are not literal, but refer to God's presence come down (= 'cloud' and Lord 'come down'), and meeting with the welcome parade (= 'in the air').
V15 assures us that in the parade there will be two types of people: those awoken from sleep and those who were among the living at the point of Jesus' return. There is no advantage to either - the sleeping will be raised to be part of the welcome.
Note the concept of sleeping - that is the Christian understanding of those in Christ who physically die among us. In the grand scheme they are simply sleeping, in transition, passing through. They are not caught in a cul de sac, but are sleeping until new resurrection life. We know this because Jesus died and was raised. He has completed the journey and now calls back to us.
Our faith puts us in Christ, and He will hold us not in death as such, but in sleep. That is the difference between Christian understanding and a secular viewpoint, so we do not grieve in the same way (v13). We have hope that looks forward, a hope that is only possible with the risen Christ.
With that hope, why do we not simply all have a huge suicide pact to jump straight to the end? That is because we not only believe in risen life after death, but we also believe in life before death. Life has God-given purpose, there are things for us to do. This is true for every life, which is why we reach out to even the most marginalised and excluded ... praying God's Kingdom come, on earth as it is in heaven, wanting to see Kingdom life all across our city.
We want to see that, and work in anticipation of it, looking forward to its fullness on the day of God's choosing expectantly, eagerly and prepared (5:1 - 3). That day will be an unmistakable event, with full fanfar, flags, the works! A day when we can rush out with many to line the route, standing shoulder to shoulder with those previously departed. In the line will include not just the high and mighty, not just the 'successful', but also those from the dis-enfranchised and the most disturbed, but nevertheless people who found themselves in Christ, put back together to welcome Jesus as King.