Boeing on Tuesday celebrated the certification of its latest passenger plane, the 737-7 MAX, 15 years after it announced the type and seven years after the first model rolled off the production line.

The US Federal Aviation Administration (FAA) certified the plane on Monday, saying its decision “reflects years of sustained work to resolve complex technical issues and complete a thorough review of the airplane’s design and supporting safety analyses.”

Many of the 737-7’s problems were also present in the 737-8 MAX, which suffered fatal crashes in 2018 and 2019 due to faulty software.

Boeing built the first 737-7 in 2018 and planned for it to enter commercial service a year later. After the 737-8 crashes, regulators grounded the plane while Boeing worked to fix it, leaving the aerospace company without resources to work on the 737-7. Boeing also had little incentive to prioritize the 737-7, as only Southwest Airlines wanted it at that time.

The craft’s limited appeal is due to its unusual configuration, which sees it capable of carrying 172 passengers up to 3,850 nautical miles. That makes it the smallest model in the 737 family, while also enjoying the longest range.

Boeing pitched the 737-7 as larger and longer-legged than the Airbus A319neo, the smaller version of the A320. The littlest 737 is also the closest thing Boeing has to a regional jet, the class of aircraft with up to 150 seats. Airlines sometimes use long-range regional jets to explore new routes. Airbus and Embraer dominate the market for such planes. The 737-7 gives Boeing a possible competitor that airlines may find appealing as it can be adapted to other missions.

US airline Allegiant signed up to buy the model in 2022.

As Boeing worked to get all of its 737 MAX models back in the air, it found problems specific to the 737-7 – notably an issue with anti-icing systems that could cause excess heat to build up on engine inlets.

Boeing sorted that and other issues out to the FAA’s satisfaction, and is now ready to sell the 737-7. It may be ready to crank them out at quite a rate, too, as its most recent shipment data revealed it built 129 737s last quarter.

It’s been a good few weeks for Boeing, which in July announced it had completed the final certification flight of the 737-10, the largest of the MAX generation planes. The FAA now gets to decide if Boeing got it right.

The company’s major piece of unfinished business is now the 777X, the new version of its largest widebody. Boeing planned to deliver the 777X in 2020, but myriad complications saw it miss that deadline and the company now hopes the new plane will fly in 2027.

Even if Boeing does win approval for the 777X next year, it will have a problem with the type because it built over 20 test aircraft using designs the FAA didn’t approve. Those planes will need significant modifications before airlines can put them into service. Carriers are understandably reluctant to buy those planes, leaving Boeing with a potential fleet of duds it can’t sell.

The American plane-maker can at least bask in the satisfaction of seeing its great rival Airbus announce tests of folding wings for its future planes, as Boeing used that design in the 777X. ®