The new plane, known as the 737 MAX 10X, would offer more range to Boeing's current fleet of single-aisle jets, rivalling the Airbus A321neo, which will carry up to 240 passengers.
Certification of the MAX 8 comes two days after the next re-engined 737 variant, the MAX 9, rolled out.
The aircraft is now set to undergo systems checks, fuelling and engine runs on the flight time before flight testing commences in the next few weeks.
"The question to ask is, would Boeing even be considering the (737) MAX 10, if it weren't for the A321neo", he said at the ISTAT Americas air finance conference.
The skies may have been gray at Boeing's Renton plant today, but the mood was sunny - thanks to the rollout of Boeing's first 737 MAX 9 jet.More news: BritBox Launches in US With the Intent to "Surprise and Delight"
More news: Soy may improve survival rates in some breast cancer patients
More news: Flock of Turkeys Circle Dead Cat in Weird Ritualistic Dance
"Boeing is actively engaged in discussions with customers about the 737 MAX 10X", Boeing's Randy Tinseth said in a company blog post. "Our primary focus is delivering an aircraft that has the legendary reliability our 737 customers depend on, plus the optimized flexibility and range capability they desire".
The 737 MAX 8 reduces fuel use and Carbon dioxide emissions by an additional 14 percent over today's most fuel-efficient single-aisle airplanes. 737 MAX 9 is the flawless answer to the need for growth while maintaining maximum airline profitability.
It says that by stretching the 737 MAX 9 fuselage and adding 12 seats, it would match capacity of the A3212neo which carries 185 people or over 200 in denser configurations.
Meanwhile Boeing's 737 Max 8 is due to begin delivery in the second quarter of this year, which will be followed by the smaller Max 7 and higher-capacity Max 200.
The 737 MAX family is the fastest-selling commercial-aircraft family in Boeing history, accumulating orders for more than 3,600 aircraft to date from 83 customers.