Leeham News and Analysis is&nbsp;the premier source for in-depth aerospace and airline industry insights. Its team of highly experienced journalists and analysts provides coverage of topics including airframe and engine manufacturers, the aerospace supply chain, airline fleet planning, future technology, and maintenance, repair, and overhaul.
<a href="https://leehamnews.com/">LNA</a> is led by Scott Hamilton, founder and managing director of the Leeham company, and aeronautical and economics analyst Bjorn Fehrm. <a href="https://leehamnews.com/subscriptions/">Subscribers</a>, who include C-suite industry leaders, have exclusive access to its expert coverage. Our&nbsp;news teams are increasingly collaborating on this content, making some of it available across AIN platforms, including our <a href="https://www.ainonline.com/futureflight">FutureFlight</a> channel, weekly newsletter, and show daily publications.
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Leeham News and Analysis Staff

Boeing has received Federal Aviation Administration (FAA) approval to proceed with type inspection authorization (TIA) phase 4B certification testing for the 777X, a critical piece of securing type certification of the long-delayed widebody airliner derivative. The milestone was revealed to&nbsp;Leeham News and Analysis&nbsp;in a June 6 interview&nbsp;with Stephanie Pope, chief executive of Boeing Commercial Airplanes.
“This authorization unlocks the largest remaining portion of our flight&nbsp;test with the FAA that we&nbsp;can now go execute," she explained. "It enables further&nbsp;avionics and stability and control testing, as well as human factors flight&nbsp;testing."
According to Boeing, TIA-4B flight testing on the 777X&nbsp;is not yet complete, but the bulk of work in other&nbsp;phases of the TIA process is done.
"There're five TIAs that we have to work through," Pope said. "4B is the last with&nbsp;what I'd say is a significant amount of work, predominantly focused on systems&nbsp;like avionics. We just got the approvals to go complete that work, which&nbsp;is a big milestone."
<h2>Heightened Scrutiny</h2>
TIA is typically a one-step authorization, but the FAA decided to grant it in stages for the 777-9 aircraft. This was as a result of the agency stepping up scrutiny of Boeing's aircraft development programs following the 737 Max crashes of 2018 and 2019.
Type certification of the 777X is not imminent. Boeing maintains that it is on track to achieve that milestone&nbsp;next year, about seven&nbsp;years after the company originally expected to start&nbsp;delivering 777-9s to customers.
Precisely how much longer Boeing's 777X flight-test program will last is unclear. The FAA will likely require hundreds more test points before issuing a type certificate.
Four 777X test articles have flown thousands of hours to date, though the test fleet was grounded for several months starting in August 2024 due to thrust-link stress fractures found during inspections. Boeing maintains that redesigning and replacing affected components has resolved the thrust link fatigue issue.
Certification of the 777X is viewed as critical to Boeing's efforts to regain its competitive position in the large twin-aisle aircraft segment. It has been losing ground to the Airbus A350-1000, which entered service in February 2018 as the largest member of the A350 family.
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