And to the person who said it was normal to have full opposite deflection of the ailerons - well that may be. But I've been on a large number of DC-9 flights and never saw that before. And they did pull out of line. Whatever, it did no harm to just calmly point and speak out. Maybe it did some good.
In general, full opposite deflection of ailerons is preferable to full deflection in the same direction.
Good on them for pulling out of line, I would do the same if somebody told me I had a problem with my aircraft. Not sure why they thought running flaps in and out would cure an aileron problem, maybe just do something to calm down an anxious passenger?
Elevators work the same way:
