While service and perks have steadily eroded over the years on domestic flights, transcontinental service remains the arena of one-upmanship among competing airlines — especially those vying for forward-class fliers.

Delta Air Lines recently announced the addition of lie-flat seats on all flights between New York’s JFK airport and Seattle, Los Angeles and San Francisco by next summer

Last month, American Airlines began flying daily between two California hubs and JFK with its new First Class service in which each lie-flat seat has aisle access. Business-class seats also recline to beds.

.In December, United Airlines introduced flat-bed seats on all flights between JFK and Los Angeles and San Francisco. Called “Premium Service,” the perks that will be available include 28 BusinessFirst seats with the kind of service, including multicourse meals, usually reserved for international flights.

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Whether legacy or boutique airlines, all carriers have been newly challenged for the lucrative coast-to-coast business — considered glamorous based on the number of movie stars and moguls who fly them — by JetBlue.

The traditionally low-cost carrier has just introduced JetBlue Mint, a premium cabin on select flights between JFK and Los Angeles. In the front cabin, all 16 seats fully recline, and four of them feature doors that can be closed to create private suites. Tickets start at $599 one way. All flights on the Los Angeles route will offer the cabin by Aug. 3, and Kennedy-to-San Francisco service will start Oct. 26.

JetBlue’s entry has already scrambled forward-class fares, according to George Hobica, founder of Airfarewatchdog.com. A few months ago, he paid $2,500 for a business-class transcontinental fare on American Airlines, a rate that dropped to around $1,200 on some flights, especially off-peak, since the launch of JetBlue Mint.

Interestingly, Hobica has observed few fliers actually reclining when they have the chance. “Unless it’s a red-eye flight, I find very few people actually recline,” he said. “It’s almost like the hotel gym where you have to have it, but very few people use it.”