Wouldn't be too surprising. But then again, I know a couple Spirit guys that have apps out at Delta and United. The bottom line still remains which is that Virgin/Spirit/JetBlue/Frontier are still Airbus LCCs and the pay/retirement/QOL package long-term is still far better at a legacy like AA/UAL/DAL. As from my personal experience, I've only flown with two CAs that were actively looking to leave. The majority seem to be staying. Of course, that kinda thing is always subject to change.