Why does Alec ask Mark to come to the cockpit in Chapter 63? What does Mark discover on his way there?

Alec tells Mark to come to the cockpit to watch him fly, because they will take Deedee to Asheville if it is the last thing he does. Mark goes to check on Trina and Deedee, who are huddled together, pointing overhead. Deedee points to the ceiling and says the boogie man and his friends are up there