The race for ever-fancier aircraft interiors is running headlong into the strict demands of regulators, delaying cabin upgrades just as airlines seek to cash in on booming demand from well-heeled travelers.

Safety agencies around the world are trying to grapple with increasingly complex, and highly customized, seat and suite designs that can vary significantly from one airline to another. There are enclosed cabins with sliding doors to consider, seats positioned at different angles and intricate cabinets that all make flying more enjoyable — but create potential risks for passengers in the event of emergencies.