St. Thomas Aquinas tackles this in his commentary on 1 Thessalonians, here is the quote
Then when Paul says, and the dead in Christ will rise first, he mentions the order that the resurrection will follow. In doing so he makes three points. First, he treats the resurrection of the dead; secondly, he considers the meeting of the living with Christ (4:17); finally, he refers to the happiness of the saints with Christ (4:17b).
Because of these words some people believed that the last people alive would never die, as Jerome mentions in his letter. For Paul has said, then we who are alive… shall be caught up together. It might seem that there would be no other reason for distinguishing the living from the dead. But on the contrary: “We shall all indeed rise”] (1 Cor. 15:51). “For as in Adam all die, so also in Christ shall all be made alive” (1 Cor. 15:22). “So death spread to all men” (Rom. 5:12).
And so I say that some shall be alive at the time when Christ shall come for judgment, but in that moment they shall die and immediately afterwards they will rise. Because of the minimal time involved they are regarded as living. But then another problem presents itself because it is said: and the dead in Christ will rise first and then we who are alive. So it seems that the dead will rise before the living will meet Christ, and that the living will die when they meet Him. So it appears that some will rise ahead of these others, and that there will not be a resurrection of everyone at the same time. This is contrary, however, to what is found in 1 Cor. (15:22): “In a moment, in the twinkling of an eye, at the last trumpet.”
I wish to point out that there are two opinions on this matter. For some say that the resurrection will not take place at the same time for everybody, but that first the dead will come with Christ, and during the time that Christ is coming the living will be taken up into the clouds and they will die and rise while they are being taken up. So that what is said to happen in a moment may be understood as occurring in a brief amount of time. And if you insist that it will happen in an instant, then it should not be applied to the total resurrection of all, but rather to the resurrection of individuals, for every individual will rise in an instant. But there are others, who maintain that everyone will rise at the same time and in an instant. They feel that where Paul says will rise first, he denotes the order of dignity, not the order of time. This does seem difficult to maintain for many still alive will suffer in the persecution of the Antichrist and be more distinguished than those who had died before.
And so it seems necessary to answer the question in a different way, saying that all will die and all will rise at the same time. For the Apostle does not say that the dead will rise first and then the living, but that the dead will rise before the living will meet Christ. Therefore he is not speaking about the resurrection in terms of the order in which they shall rise, but of the order in which they will be taken up to meet Christ. For when the Lord does come, first those who are found alive will die and then, immediately together with those who had died before, they will rise up and be taken up into the clouds to meet Christ, as Paul clearly says.
