(warning: spoilers ahead)
In Red 2, During the final scenes, we see Frank and Marvin crash with the bomb in the helicopter. Then Frank and Sarah get to the plane, where Bailey is waiting for them. After a brief exchange and after Sarah leaves, Bailey tells frank to take the bomb with him and leaves on the plane.
We do not see Frank put the bomb in the plane, yet that's where it is after Beiley leaves. So, how did he do it?