The wing tips of a large aircraft, for example, might move up and down through more than six feet relative to the fuselage when the aircraft goes from the ground, where the wings only have to support their own weight, to flight, where they support the weight of the entire aircraft.
According to "
DESIGN-CENTERED INTRODUCTION TO AEROSPACE ENGINEERING
12. STRUCTURES & MATERIALS
http://www.adl.gatech.edu/classes/dc...tur/dci08.html
I think 6-7 feet are more likely than 20.