By Eric M. Johnson

RENTON, Wash. (Reuters) -Boeing Co’s 737 MAX 10, the largest member of its best-selling single-aisle airplane family, took off on its maiden flight on Friday, in a further step toward recovering from the safety grounding of a smaller model.

The plane completed a roughly 2-1/2-hour flight over Washington State, returning to Renton Municipal Airport near Seattle at 12:38 p.m.

The first flight heralds months of testing and safety certification work before the jet is expected to enter service in 2023.

In an unusual departure from the PR buzz surrounding first flights, the event was kept low-key as Boeing tries to navigate overlapping crises caused by a 20-month grounding in the wake of two crashes and the COVID-19 pandemic.

Boeing’s 230-seat 737-10 is designed to close the gap between its 178-to-220-seat 737-9, and Airbus’s 185-to-240-seat A321neo, which dominates the top end of the narrowbody jet market, worth some $3.5 trillion over 20 years.

However, the market opportunity for the 737 MAX 10 is constrained by the jet’s range of about 3,300 nautical miles (6,100 km), which falls short of the A321neo’s roughly 4,000 nm.

Boeing must also complete safety certification of the plane under a tougher regulatory climate following two fatal crashes of a smaller 737 MAX version grounded the model for nearly two years – with a safety ban still in place in China.

Boeing has carried out design and training changes on the MAX family, which returned to U.S. operations in December.

Boeing Commercial Airplanes CEO Stan Deal said the company is producing about 16 737 MAX jets a month at its Renton factory.

Boeing is working on safety enhancements for the 737 MAX 10, including for its air data indication system and adding a third cockpit indication requested by European regulators of the “angle of attack,” a parameter needed to avoid stalling or losing lift. Deal’s comments were provided to the media via a pool reporter inside a Boeing aircraft delivery center.

“We’re going to take our time on this certification,” Deal said.

While the smaller MAX 8 is Boeing’s fastest-selling jet, slow sales of the MAX 9 and 10 models have put Boeing at a disadvantage to the A321neo.

Boeing has abandoned plans to tinker with the 737 MAX 10 design, but is weighing a bolder plan to replace the single-aisle 757, which overlaps with the top end of the MAX family.

Even so, Boeing says it is confident in the MAX 10, and it is stepping up efforts to sell more of the jet, with key targets, including Ireland’s Ryanair.

Customers include United Airlines with 100 on order. Although sources say United is weighing a new order for at least 100 or even up to 200 MAX, its requirement for large single-aisles will be served by Airbus – reinforcing the market split.

The flight, watched by dozens of employees but virtually no visitors as Boeing sought to downplay the event, showcased a revamped landing gear system illustrating an industry battle to squeeze as much mileage as possible out of the current generation of single-aisles.

It raises the landing gear’s height during take-off and landing, a design needed to compensate for the MAX 10’s extra length and prevent the tail scraping the runway on take-off.

(Reporting by Eric M. Johnson in SeattleAdditional reporting by Tim Hepher Editing by Leslie Adler, Aurora Ellis, Mark Potter and Cynthia Osterman)

---