United’s new lay-flat seats are a brilliant way to upsell the economy class

Few sectors of the economy show the growing divide between the haves and have nots more than the airline industry, which is increasingly catering to high-income flyers in an effort to squeeze as much revenue per available seat mile as possible. United, which just announced newly designed economy seats you can lie flat and sleep on, found a clever way to appeal to everyone by bringing the couch to coach.

This week, the airline announced what it calls “United Relax Row,” a row of three...