U.S. regional airlines seek to persuade regulators to ease experience requirements for hiring many future co-pilots, while proposing to significantly enhance training and supervision once the aviators start flying passengers.

The initiative lays out a potential alternate path to the cockpit for starting pilots that includes time sitting in airliner jump seats as observers, more-frequent proficiency checks by carriers, beefed-up stall-recovery training and a year or more of formal mentoring by senior pilots.

Primary...