Adin,

I was the welding instructor for UAL for many years, but that was a long time ago.  (Left in 2003)

They test and do recurrent testing in accordance with AWS D17 as you might suspect.

Back in my time all the welder testing was done at SFO in the giant turbine overhaul shop, but I know that sense the Continental merger they have moved at least some of that to the Continental Mantainence base in Houston.

The new hire practical test “used to be”  a fabrication of an an austinetic stainless steel “box” that had various CJP grooves and attaching jewelry that required argon backing.   The base metal was about .050 for that assembly. The box had instructions, but if the welder was inexperienced it was possible to go too fast and assemble the weldment without getting the last weld in.... Sort of a common sense “don’t weld yourself into a corner thing..   There were also some thick to thin fillets,,, like .040 to .125 to make sure you understood how to avoid burn-thru.

The written exam was cake.... although there were a fev very basic EB questions tossed in.  Just basic process question and symbols.

The evaluation of the test pieces was pretty subjective (I never liked that part),   Hopefully that has changed.

If you are capable of making CJP on thin stainless and aluminum, can follow basic details and symbols and understand terms and definitions it shouldn’t be overwhelming.

If your “test kit” has a cooper purge/backing box, use it every place you can.  If plain copper bar is provided, think about where you can use it as a heat sink, (thin to thick fillets)

If anything else comes to mind I’ll come back and post again.