Delta Air Lines will put its new premium economy seats on its entire international widebody fleet by 2021. US carriers are playing catch-up with premium economy and Delta only announced its new Premium Select cabin in 2016.  The airline introduced the cabin the following year on its Airbus  A350s and this year is rolling it out on its Boeing 777s. It is now discovering what airlines in other parts of the world have found: passengers like the concept. Delta estimated last week that an 8 percent gain in premium seats — including premium Select, Delta One and Comfort Plus — had produced a 20 percent increase in revenue in the second quarter. WATCH Slipping into LAX at sunrise. Delta President Glen Hauenstein told reporters and analysts on a recent conference call that the airline continued to be excited about the future as it drove better brand loyalty and customer segmentation. Hauenstein said the airline would continue to expand premium seat numbers and Premium Select would be available on the entire widebody fleet from 2021 because "people want to buy these products and services from us.'' "And quite honestly, we haven't made it that easy for them,’’ he said. “Over the next months and years, we're going to make it easier and easier with more and more ways to buy these products and services, and we see that as a real growth opportunity.” Delta premium Select features 19-inch wide seats with a pitch of 38 inches, adjustable leg rests and headrests, a 13.3-inch high-resolution in-flight entertainment screen and in-seat power. Customers pay about double the price of an economy ticket but get other perks such as better food and drinks as faster check-in. READ: Delta shuns economy class crush. On the question of whether Premium Select was cannibalizing more expensive business class fares, Hauenstein said there had been robust demand for the Delta One product. Premium Select had now been introduced into 50 percent of Pacific markets and there had been no real degradation in demand for premium products, he said. Instead, consumers and corporations with travel policies only allowing coach travel had been trading up. “As we continue to roll out different ways to buy those products, we will see, I think, another explosion in demand as other customers will use their miles to sit in the cabins they want,’’ he said. “And I think the ability of our frequent flyers to choose where they want to sit after they buy the ticket is really going to be something that's going to generate a lot of great products and services for customers as well as revenue for the airline.’’