From 1 Thess. 4:
16 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:
17 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.
From Rev 6:
9 When He opened the fifth seal, I saw under the altar the souls of those who had been slain for the word of God and for the testimony which they held.
11 Then a white robe was given to each of them...
Are these passages both describing the same event?
Note this would make both prior to the sixth seal (Rev 6:12)