I have never been myself. I have been to mnl a couple of times and its usually the same situation where coach is oversold by 30 and First has a lot of open seats. many of my coworkers go to GUM and our priority is just above S4 for AS/QX airline employees. I could be wrong but i think they put in S4 pass riders in first class. So even if coach is oversold you wont have problem getting on. At least that is my experience .