The lie-flat wars are heating up.Over the weekend, Delta Air Lines made a notable schedule update for its transcon route between Boston (BOS) and Los Angeles (LAX). Beginning on July 7, the carrier will deploy a Boeing 757-200 on the 2,611-mile cross-country jaunt, instead of the previously scheduled Boeing 737-800, confirmed by Cirium schedules and the carrier’s website.Delta didn’t change the route’s frequency — it’s still up to four times daily — but the aircraft swap spells great news for those sitting in the pointy end of the plane.Want more airline-specific news? Sign up for TPG’s free new biweekly Aviation newsletter!That’s because Delta’s internationally configured Boeing 757 sports 16 lie-flat business-class pods arranged in a 2-2 configuration, compared to the standard domestic first-class recliners that the previously scheduled 737 offers.Delta One on the Boeing 757-200 (Photo by Zach Griff/The Points Guy)In addition to lie-flat biz, the 757 is outfitted with 44 extra-legroom Comfort+ seats, as well as 108 standard coach ones, in a 3-3 arrangement.Along with the upgauge, Delta will market the service as one of its signature Delta One transcon routes.Coach on Delta’s Boeing 757-200 (Photo by Zach Griff/The Points Guy)If the current schedule sticks — anything can change, especially due to the pandemic — it’d mean that every Delta transcon from BOS to LAX would be outfitted with a true biz cabin.That’s quite the break from Delta’s thinking roughly a month ago. In mid-April, Delta pulled all the Boeing 757s from the BOS-LAX route, and replaced them with 737s. The Atlanta-based carrier explained to TPG that demand didn’t warrant lie-flats, but Delta was “in a position to adjust quickly to demand,” if and when it returns.Sign up for our daily newsletterEmail addressSign upI would like to subscribe to The Points Guy newsletters and special email promotions. The Points Guy will not share or sell your email. See privacy policy.Now, four weeks later, it would appear that demand for the fancy biz seats is expected to return come the summer. But that might not be Delta’s only motivation to upgauge the route so quickly.Two weeks after Delta pulled lie-flats between BOS and LAX, American Airlines and JetBlue announced another slew of new routes and increased coordination as part of the Northeast Alliance, which includes — as you might’ve guessed — service between Boston and Los Angeles.On April 21, American announced that it’ll deploy its premium-heavy Airbus A321T on the aforementioned route beginning on Nov. 2. The plane, outfitted with just 102 seats, is arranged in a three-cabin configuration, with 10 first-class pods, 20 business-class lie-flat beds, and 72 coach seats, half of which are designated as extra-legroom Main Cabin Extra.More Northeast Alliance: 7 key takeaways as American, JetBlue expand again in NortheastAs AA and JetBlue cozy up, they’re planning to offer a premium transcon experience and metal neutrality on the routes between New York and Boston and both Los Angeles (LAX) and San Francisco (SFO). JetBlue will fly its Mint-equipped Airbus A321s, and American will use its Airbus A321T.Now, with Delta deploying a 757 on the route, the carriers will go head-to-head to capture the premium demand for flights between the coasts.United, on the other hand, hasn’t (yet) responded to the competition. The Chicago-based carrier is still planning to fly Boeing 737s between BOS and LAX, though the BOS to SFO route is slated to be upgraded to a lie-flat equipped Boeing 757 on Aug. 1.Delta One on the Boeing 757-200 (Photo by Zach Griff/The Points Guy)Boston isn’t the only city in the Northeast corridor feeling the Delta love. Flyers traveling from Washington, D.C. to Los Angeles are also in for an upgrade.As part of the latest schedule update, Delta will fly its internationally configured Boeing 757-200 between Washington Reagan National (DCA) and LAX on its one daily frequency beginning on July 7.