Some of you already know that I have quite a large United Airlines memorabilia collection that includes complete dining set ups going all the way back to the 1940's. I've even loaned United several pieces for various displays they occasional put up or contribute to.
Most of my collection was derived from various airline memorabilia shows and sales across the country (pre-eBay), and more recently eBay.
For current or recent items, you can often find Surplus Property Sales at various airlines that are held every so often (usually at a major hub airport facility or nearby warehouse). These Surplus Property Sales include everything under the sun...onboard dinnerware, headsets, old-style amenity kits, even mechanical parts and service items. I don't personally purchase much from these as often the minimum quantities are too high for me. But outfits like Fish Eddies probably pick up quite a lot from these directly or from the many re-sell vendors that purchase from these Property Sales.
I also know for a fact that other vendors purchase airline flatware for re-sale to the general restaurant supply business, as I've reported here before that I know of several restaurants where they have United flatware mixed in with their other mis-matching flatware. I think these supply houses sell this stuff to outlets that don't care about what their flatware looks like and are just looking for cheap, durable stuff. Places like soup kitchens and cafeterias and senior social services centers. As well as the odd restaurant that doesn't give a poop about matching flatware.
Fast Eddies could be getting theirs from eBay too though. I often see sealed bags of 48 forks or (yes, metal) knives or whatever from United for sale on eBay and the whole bag of 48 goes for only like $6.00 or so. Now whether those are from a legit Property Sale or if they "fell off a truck" is anyone's guess.