Boeing is close to getting FAA certification approval on the 737-7s and the go-ahead to start formal flight-testing of the 737-10—steps that could see deliveries of the last two 737 Max variants start in early 2024 and early 2025 respectively, sources with knowledge of the programs tell Aviation Week.

The long-awaited 737-7 certification is on track for year-end at the latest and could come as soon as next month, the sources said. The timeline, which is in line with statements made earlier this year by 737 SVP development programs and customer support Mike Fleming, should allow deliveries to get underway to launch customer Southwest Airlines by early 2024. The airline said earlier this year that its notional plan saw certification in 2023, but it did not expect deliveries to start before 2024.

On the 737-10, Boeing is about 70% through a list of items the FAA has required before the agency grants type inspection authorization (TIA), the milestone which marks the start of flight testing for certification credit. Boeing has been working with the FAA to complete system safety assessments and newly required human factors assumptions validation.

Assuming TIA is granted by year-end and flight testing goes with few major surprises, Boeing would start 737-10 deliveries in the first quarter of 2025, the sources said.

Officially, Boeing has offered little beyond vague outlines of its notional certification timelines. Fleming told reporters in May that Boeing’s latest plans assume 737-7 certification and 737-10 TIA “this calendar year,” followed by 737-10 certification in 2024. But, he added, the new certification environment means plans must remain fluid and nothing is final until the FAA says so.

Speaking during the company’s third-quarter earnings call Oct. 25, Boeing executives said nothing has changed on 737-7 or 737-10 timelines but declined to pinpoint specific dates for the key milestones.

“The FAA makes that call and we’re going to give them all the flexibility they need,” CEO Dave Calhoun said.

“In terms of the certification milestones that we have in front of us ... there’s been no change,” added CFO Brian West. “There’s really nothing to say other than there’s a lot of people hard at work.”

Calhoun reiterated that outstanding deliverables are mostly “design assurance documentation” required by a late 2020 law that pushed through a series of certification reforms. Among the new requirements: validating system safety assessments with certain human factors-related assumptions, such as a pilot’s anticipated response to an alert or warning. The 737-10’s certification’s scope, already notably different from its 737 MAX predecessors due to several changes being introduced for retrofit fleet-wide, has expanded some in recent months to cover more required changes.

The FAA in September issued an exemption that will permit 737-7 certification approval without new yaw-damper software that Boeing and the agency determined was needed to meet the latest regulations. It will be introduced and approved on the 737-10 and, like a new angle-of-attack (AOA) monitoring system, eventually retrofitted at Boeing’s expense.

Meanwhile, the fifth production 737-10, built for United Airlines, is participating in the latest phase of Boeing’s on-going ecoDemonstrator technology demonstration effort. All other 737-10 test aircraft are inactive.

The only known active 737 MAX family test aircraft, a 737-8, is engaged in systems tests. It is not clear whether the work is linked to upgrading the 737 MAX family with the enhanced AOA system or other tasks such as the development of the new yaw damper software.