SEATTLE - With more than 3,600 Boeing 737 MAX jet airliners on order, one could wonder why Boeing wants to build an even longer 737 with more seats.

The reason is to meet the competition. Airbus has enjoyed an advantage and an order bump because it's A321 and with its so-called New Engine Option (NEO) that advantage against the MAX is growing. That plane able to attract buyers such as Delta Air Lines, with the ability to fit in more passengers over the largest member of the MAX family, the MAX 9.

A Boeing 737 MAX 10 intended to go head to head with the A321 NEO. "We think the ten really addresses that customer who wants the capacity in the market, capacity that makes a difference with them," says Randy Tinseth, Boeing's V.P. for marketing who deals directly with airlines to help the company to help figure out what airlines want in a plane.

The MAX 9, which rolled out of the factory in Renton Tuesday, will carry 178 passengers in a typical two-class configuration -- first and coach. Keith Leverkuhn, Boeing's Vice President and General Manager for the 737 MAX program, says the MAX 10 can carry another 11 passengers in a two-class configuration and as many as 230 passengers in an all-coach configuration that can be used by charter and tour operators.

But there's another attraction. Boeing claims airlines will enjoy 5 percent lower costs over the A321.

"Anyway you slice it, it's better in trip cost, seat mile costs," said Leverkuhn. He says the plane would still be able to fly across the continental United States with a range of more than 3,100 nautical miles. It also means one of the biggest 737 customers, China, could use the MAX 10's added capacity and still fly from east coast cities like Shanghai far into the western part of the country.

The plane would start flying for the airlines that buy it in 2020.

But is there interest?

Boeing's Tinseth just back from speaking with leasing companies at the International Society of Transport Aircraft Trading conference in San Diego, California. "It helps the MAX family grow and the order base grow," says Tinseth of the ten.

A MAX 10, if Boeing decides to build it, will add a fourth model to the Boeing 737 lineup, and would be the company's biggest 737 ever made. Right now the MAX lineup, like the 737 Next Generation lineup before it, offers a 737-MAX 7 with 126 seats, the biggest part of the order book, the MAX 8 with 162 seats; and the MAX 9 at 178.

The MAX 10, as currently envisioned, would be 66 inches longer than the MAX 9 to fit in those 11 more seats. That will also require the plane to lift up higher on takeoff, so the tail doesn't strike the ground. Leverkuhn says work is underway to create a new landing gear that can still fit into the existing wheel wells.

Boeing continues to talk to airlines globally to see if the MAX 10 will be launched The company also expecting FAA certification of the first 737 MAX 8 soon.

"The whole purpose of the ten is a tactical move," says analyst Scott Hamilton with Leeham and Co. "To prevent any more strategic inroads into certain airlines that are exclusively Boeing customers."

Hamilton says his firm has closely studied the two planes and says Boeing may only sell a few hundred MAX 10s. He says with auxiliary fuel tanks the Airbus jet could get a higher range, Boeing says it's expected MAX 10 range is plenty as intended. He sees the MAX 10 and the A321 NEO comparable in their seat efficiency.

One of the airlines he points to is Alaska, which will get some new A321s to test out as part of its merger with Virgin America. Alaska airlines has been one of those all Boeing carriers. The extended range 737-900 is a popular plane with Alaska, which also has MAX 9s on order with can fly 600 miles further.

"It helps the MAX family grow and the order base grow," says Boeing's Tinseth. As the company works to keep new orders coming in and its dog fight with Airbus continues.