A bag in a bag in a bag. An empty bag.

I flew on British Airways to Lisbon and back this last week.     In a vestigial remnant of providing us with food service, they gave us sandwiches.    To make life easy for cleanup they provided a trash bag.

Or put it this way.

They provided a plastic bag in a plastic bag in a plastic bag.   And the (innermost) bag was empty.  

There was a bag with tissue and stuff in it.   The bag was of course plastic.   Inside this bag one of the items was a small plastic bag.  In that, very neatly folded up, was a plastic trash bag.

So yes, they gave me a plastic bag in a plastic bag in a plastic bag.   And the plastic bag was empty.