There have been a lot of experimentals with variable wingspan.

One you will find here

http://www.aviafrance.com/4806.htm

KH

schrieb im Newsbeitrag
oups.com...

when I look at my eyeglass case, I see two closely overlapping
wing-type shapes that are being pulled apart for opening.

why would it not be worthwhile to extend wings this way for landing and
departure?

/iaw