Hi team! I just ran into the same issue- 120W power supply on a Delta flight, the power outlet light just goes from green to dark (assuming it shut itself off).
I read through the thread and have purchased a 90W power supply to try next week- theoretically this should put enough power through to my laptop to extent its life right? It wont be able to keep up when it's running full bore- but maybe eek out another half hour to hour of life?