From CNBC:

Frontier Airlines introduces UpFront Plus, a new offering to block the sale of middle seats in the first two rows of its Airbus planes. Prices start at $49 for bookings made by March 20. Other airlines, from budget carriers like Spirit to major players like Delta and American, have also been exploring ways to generate more revenue by segmenting their cabins and adding fees for premium services.

This new offering by Frontier is not a new seat, but rather a different spacing arrangement with extra legroom. Budget airlines like Frontier rely heavily on additional fees for services like seat selection and carry-on bags, with nonfare revenue per passenger increasing by 1% to nearly $74 last year. Airfare revenues fell by 22% to $42 per passenger on average.



Read more at CNBC: Empty middle seats, more legroom