Boeing 737-7 Reactivation Marks MAX Certification Push

While the pace of flight tests of the 737-7 and -10 has waxed and waned over the past two years, a new uptick in aircraft activity indicates Boeing may be entering the final stretch of certification tests for the long-delayed pair of MAX family derivatives.

The re-activation of the sole 737-7 development aircraft, 1E001, with a flight test on Oct. 6, marks a significant sign of acceleration for the certification effort which stalled more than two years ago over the need for a redesign of the engine anti-ice (EAI) system and associated nacelle inlet structure.

The return to test of the 737-7 follows a ferry flight on Aug. 11 to Boeing Field, Seattle, from Moses Lake, Washington, where the aircraft had been in storage since June 2023. At the same time, tests with the stretched 737-10 development fleet are also picking up with the second aircraft, IG002, flying from Seattle to Roswell, New Mexico, on Oct. 7, for the start of a new phase of certification work.

Sister 737-10 test aircraft, 1G001, has been flying consistently throughout 2025 and has accumulated almost 1,100 flight hours over 319 sorties since its first flight in June 2021. The third -10 aircraft, 1G003, also resumed flight tests on Oct. 6, having last flown in early August. Test aircraft 1G003 has built up 253 hrs. of flight time over 80 flights, while 1G002 has amassed 424 hrs. of flight time over 150 flights.

The surge in activity comes less than a month after Boeing CEO Kelly Ortberg said the company was closing in on a finalized EAI design and reaffirmed the final pair of 737 derivatives remain on track for certification and deliveries starting in 2026.

Speaking at the Morgan Stanley Laguna conference Sept. 11, Ortberg said, “At the last earnings call [in July], we slipped the completion of the certification from the end of the year into next year. The good news is we’ve made really good progress on the design of the engine anti-ice since that time. I feel pretty good that we’re nailing that design.”

“We’re in the process right now of working with the FAA on the certification of that design, what tasks need to be done,” he added. “We’re still planning on getting that cert done next year, getting aircraft delivered next year.”

Problems with the original design of the EAI—which redirects engine bleed air to the inlet cowl—centered on the vulnerability of the inlet’s composite structure to thermal damage. Boeing has evaluated several redesigns while, at the same time, has developed in-service limitations to the use of the EAI on the 737-8 and -9 models until the new inlet is available for retrofit across all fleets.

The 737-7, which was first rolled out in February 2018, was originally expected to enter service with launch customer Southwest Airlines in 2019. The 737-10 was originally due to enter service in 2020 following its launch in 2017. This was later pushed back to 2023 after development delays in the wake of the COVID pandemic and increased certification scrutiny following the 737-8 accidents in 2018 and 2019. The further delay to 2026 has largely been driven by the EAI redesign.