I plan to use these on the plane during a long trip to Italy in Jan. and as slippers in the hotels while there.  They fold up to almost nothing and can be washed easily so will probably stay in my suitcase from now on.  They were recommended in the San Francisco Chronicle.  I did have to return my first pair for a larger size.  I wear a size 7 1/2 in shoes and ended up needing the larger size, L 8-11.  That was the only problem.