U.S. airline JetBlue isn’t underestimating the allure of lie-flat seats. The low -fare/high-frills carrier is boosting the number of daily Mint flights to more than 80 beginning early next year.   “Travelers are overdue for an upgrade of the so-called ‘first class’ offered by other airlines,” says Marty St. George, the carrier’s executive vice president commercial and planning. “In every city where we’ve introduced Mint we’ve transformed the premium travel business and boosted overall performance on the routes.”   The U.S. “transcon” (transcontinental) market is the prize here. Populated by the likes of Delta, American, United, and Alaska it’s the arena in which airlines roll out their cutting-edge ideas, especially up front, beyond the curtain separating their premium product from the “main cabin.”   Who’s best is largely a matter of taste, allegiance by corporate travel buyers and the elite frequent flyer status of customers.   What’s in undeniable demand is lie-flat seating. Here’s where JetBlue plans to introduce it or increase such service in existing markets:   Beginning January 4, 2018, JetBlue will launch nonstop Boston Logan – Las Vegas Mint service with a couple of daily nonstops.   The move follows the airline’s already announced plans to begin Mint flights between New York JFK and Las Vegas this November.   Word that JetBlue will strike at the heart of well-thought-of Alaska Airlines’ route system sets the table for some high-flying competition in the Seattle/Tacoma - Boston market this fall.  Two daily Mint nonstops get off the ground February 15, 2018.   A bit later in the year, JetBlue serves up Mint in between New York Kennedy and Seattle/Tacoma. There will be but one Mint flight on this route per day.   To illustrate how popular lie-flats are,  JetBlue adds an eleventh daily Los Angeles International – New York nonstop, as well as a fifth daily San Francisco – Boston frequency.   While the product was designed for the demands of revenue-producing business travelers who frequent the transcon, JetBlue is doubling up on leisure focused Caribbean Mint flights early next year. Second Saturday-only seasonal roundtrips are set for JFK – St. Maarten from January 13, 2018, with Boston- Aruba and Boston-St. Maarten following from February 17.   A321s will do the heavy lifting on these routes.