Helen, yes French Flags, that's what they are.

A French Fly is the flat front, of a pair trousers.

I had a bespoke tailor make a pair of kangaroo leather trousers for motorcycle riding about 32 years ago, she aksed me whether I wanted a french fly, a straight zip or a combination of both. I had never heard of that before.

I got the combination and wonder of wonders, I still fit into them and use them still.

Mick.