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.