Standing room only?

The airlines have come up with a new answer to the old question: How many passengers can be squeezed into economy class?

A lot more, it turns out, especially if an idea still in the early stage should come to pass: standing-room-only “seats.”

But even short of that option, carriers have been slipping in another row or two of seats in coach by exploiting stronger, lighter materials developed by seat manufacturers that allow for slimmer seatbacks. The thinner seats theoretically could be used to give passengers more legroom but, in practice, the airlines have been keeping the same amount of space between seats to accommodate the additional seats