The battle for America's best lie-flat seat just heated up

Two of the most competitive airline routes in the U.S. are those between New York and Los Angeles and San Francisco.

The lucrative corporate contracts and deep-pocketed leisure travelers who frequent these routes are incredibly important to carriers. So it's no surprise that each of the major U.S. airlines competes with top-notch, lie-flat premium seats.

As part of the new partnership between American Airlines and JetBlue, the two carriers are trying to bolster their position in the premium transcon market. They'll codeshare on their nonstop coast-to-coast service giving customers tons of options to choose from.

And with two of the best domestic products joining forces, Delta and United are in trouble.

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Mint is the best domestic biz product

JetBlue's Mint product is a two-time TPG Award champion. When JetBlue introduced Mint over five years ago, it took the market by surprise. The primarily leisure-focused carrier promised to disrupt the transcon business-class market. And disrupt it did.

The industry-leading hard product (including four suites) became the gold standard for those looking for the most comfort when flying coast to coast. Mint’s fresh take on the inflight food and beverage service was immediately well received. And the carrier’s service, with two dedicated and specially trained Mint flight attendants, was leagues ahead of what the competition was offering.

With fares starting at around $600 each-way, JetBlue also disrupted the pricing model. From end-to-end, JetBlue offers the best business-class product for a domestic airline.

JetBlue also nails the coach experience

In addition to Mint, JetBlue also offers a comfortable coach experience.

The leather seats are 18-inches wide and have 33 inches of pitch. Plus, all passengers can enjoy free DirecTV, high-speed Wi-Fi and access to SiriusXM.

All customers are served an assortment of drinks and unlimited brand-name snacks. And if you're feeling peckish, you can walk up to the onboard pantry and grab a snack or drink at your convenience. (Note that many of the service elements are currently limited due to the coronavirus.)

Related: Comparing premium transcon flights in the age of coronavirus

American’s A321T offers Flagship First

American Airlines' premium domestic offering is also quite special.

The carrier operates a fleet of Airbus A321s, dubbed the A321T, on these cross-country flights. With 10 Flagship First suites, 20 Flagship Business pods and 72 coach seats, it's one of the most premium commercial jets in the sky.

American's business-class product isn't as revolutionary as JetBlue's, but it's much larger and takes up a greater proportion of the plane than Mint does.

What's really cool about the A321T is that the carrier has added 10 Flagship First suites at the pointy end of the plane. It's the most exclusive commercial flight experience in the country. Many business executives and celebrities choose American because of it.

Related: Is American Airlines Flagship First worth it?

Could this mean lounge access for JetBlue passengers?

When describing the seamless experience that customers can expect from the new partnership, the airlines tout an "improved on-the-ground experience."

And one area where JetBlue falls short is that it doesn't offer or operate any airport lounges. But with American's help, it could easily bridge that gap. In fact, American Airlines' flagship ground experience is leagues ahead of both Delta and United. The latter two carriers only admit premium customers to their domestic lounges.

AA, on the other hand, invites premium passengers into their Flagship Lounges. If JetBlue Mint flyers could access Flagship Lounges, it'd only serve to strengthen the product.

AA and JetBlue both operate out of Terminal 5 at LAX. The Flagship Lounge, however, is located in Terminal 4 (American's second LAX terminal), so it'd require an easy, short walk for JetBlue passengers.

At JFK, AA and JetBlue operate from completely separate terminals that aren't connected airside. It's possible some JetBlue transcons shift terminals at JFK, but either way, lounge access at LAX would certainly be better than nothing.

Related: Listen to JetBlue's COO talk about why the carrier doesn't build a lounge

Combined, American and JetBlue offer the best transcon experience

As part of their intention to codeshare, American and JetBlue will offer the top transcon experience across the board.

In terms of onboard product, the partnership will include award-winning cabins across all levels of service — all the way from American's Flagship First to JetBlue's core economy experience. There's a seat for every price point and willingness to pay.

Consider the frequency, too. With JetBlue's recent expansion at Newark (EWR), the two carriers will offer dozens of daily transcon flights. It'll saturate the market from both New York-JFK and Newark when combined with the schedules offered by Delta and United.

Related: The best transcon US flight: Comparing American Flagship First, JetBlue Mint and United Polaris

Delta and United are in trouble

Without the American and JetBlue coordination, the "big three" plus JetBlue each competed fiercely for premium passengers. No single carrier dominated the market.

Yet now, Delta and United are in trouble. Neither carrier currently offers as robust a schedule as AA and JetBlue, nor can they compete on variety of onboard product. Plus, Delta's only got a transcon presence in New York, and United only has Newark flights.

For flyers headed to the tri-state area, having the option of flying to either JFK or EWR is amazing. If American and JetBlue indeed launch a deep frequent flyer partnership, Delta and United will really need to play catch-up.

In fact, today's move is reminiscent of what American did in the transatlantic market with British Airways. AA realized it could strengthen its hand on the there by partnering with British Airways. The pair struck an alliance in the late 1990s and have since formed a joint-venture partnership that covers their transatlantic flying.

Related: Why I'm excited about JetBlue's Mint expansion to Newark

Bottom line

The premium transcon market is one of the toughest to crack. With today's announcement, American and JetBlue are putting their best foot forward.

Between the top-notch onboard experience combined with the breadth of schedule, these two carriers are going after Delta and United.

Time will tell how they respond, but one thing's for certain — the competition just got more intense.

Featured graphic by Wyatt Smith/The Points Guy