Don't expect them from any of the US Flagged carriers, but if you're overseas you'll see them. Personally I've received them on SQ F, NH F, and LH F. I've been gifted PJ's from BA F and CX F.
They are available on most longhaul routes. On SQ you'll get them on daytime flights exceeding 7 hours and evening flights exceeding 4 hours.

SQ F is designed by Givenchy and CX F is designed by Shanghai Tang.

Here's a sampling of the SQ amenities in F over the years.