Graded Assertiveness Training Models

[MrBrico]

Hi all -
Can anyone give me a potted summary of the various types of graded assertiveness protocols taught by airlines around the world? I'm assuming there are almost as many variations as there are airlines.

My understanding is that many airlines use a derivative of Besco's original 4-step P.A.C.E.(Probe-Alert-Challenge-Emergency) algorithm. I know Qantas had their own 4-step variant on this, but has since moved on to a 5-step version.

Other airlines I believe use a 3-step 'CUS' ('I am Concerned'/'I am Uncomfortable'/'This is a Safety Issue') protocol, but I don't know what airlines teach this. Does anyone know what Korean Airlines teach?

I have read elsewhere an author suggesting that someone is teaching pilots a 6-step algorithm, but I can't confirm the source. This seems like a lot of escalation to get to the point. Does anyone know if there's an airline that teaches a 6-step protocol?

To those of you familiar with various types, which is your preferred protocol?

Thanks