Engineers with Boeing are working with the airline on the fix.
Federal investigators cut out a large section of the roof surrounding the 5-foot by 1-foot tear so they can analyze why a rivet line failed.
Teams of Southwest mechanics have placed a large green patch on the plane as it sits on a runway in Yuma. An airport official says she expects the plane to fly out within days.
A hole ripped in the plane last week as it climbed after leaving Phoenix. Inspections on hundreds of older 737s have been ordered.