United Airlines unsure what to do with lie-flat seats ordered for Boeing 737 Max 10

United Airlines ordered lie-flat premium seats for its Boeing 737 Max 10 jets years ago, but certification of the aircraft has been delayed for years. The airline is now uncertain what to do with seats designed specifically for a plane that is still not cleared to fly commercially. The prolonged Max 10 delay is disrupting United's plans to expand premium seating on domestic routes.