THE CLAIM

5) All Christians living at the time of the Second Coming will be changed into spiritual beings and meet Christ in the air.


The Biblical Proof


For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first: Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord. (1 Thessalonians 4:16-17)

Paul is writing a letter to the Christian Thessalonian Church, so "we" refers to Christians.

Behold, I show you a mystery; We shall not all sleep, but we shall all be changed. (I Corinthians 15:51)

Those that shall not sleep are Christians living at the time of the Second Coming. They will be changed into spiritual beings without "sleeping" in any grave.

There are only two type of bodies:

There is a natural body, and there is a spiritual body. (I Corinthians 15:44)

Christians living at the Second Coming have already been born as a natural body. So the only possible "change" that can be made is into a spiritual body:

Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. That which is born of the flesh is flesh; and that which is born of the Spirit is spirit. Marvel not that I said unto thee, Ye must be born again. (John 3:5-7)