Major? Do you mean such as Lufti group, KLM, BA, AF?
low fare airline? Do you mean RYR, EZY, Eurowings etc or are we talking about smaller airlines?
My view is get yourself into a large airline be it major or low cost. If you are in one of those already and command comes along then take it. Don’t jump out of a loco with a command to go elsewhere as a FO. Not worth it unless you are hell bent on long haul and are prepared to take a big pay cut. The conditions are no better in some majors v locos either.