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.
Since AIN acquired LNA in 2025, the Leeham Co. LLC and Leeham Consulting businesses remain independently owned and operated.

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.
Leeham News and Analysis is part of the AIN Media Group.
&nbsp;
&nbsp;
&nbsp;

News and developments about airplanes, helicopters and unmanned air vehicles used in all varieties of operations, including airlines, military, business, commercial, general aviation and private.

FAA Clears Boeing to Start TIA Phase 4B Testing on 777X Airliner

Milestone marks progress in efforts to complete delayed type certification

As it works to complete long-delayed type certification of its new 777X widebody airliner, Boeing has been boosted by FAA approval to start TIA Phase 4B tests.

FAA Clears Boeing to Start TIA Phase 4B Testing on 777X

2024 Corporate Aviation Leadership Summit

Kerry Lynch

News and issues relating to business, corporate and private aviation, primarily regarding turbine-engine-powered airplanes and helicopters. Subjects include aircraft, engines, maintenance, operations, personnel, acquisitions, accidents, safety, security, and training.

More In Aircraft

Bombardier Global 8000 Sets First Speed Record

Aircraft flew from Montreal to Nice, France, in just more than six hours

Argus: Bizav Flying Up in May, but Momentum Slowing

Global business aircraft activity up 3.1% in May, but June expected to be more sluggish

AINsight: No Sign of Preowned Bizjet Market Slowing

Business jet demand seems undeterred by higher fuel prices or other rising costs

Volocopter Reveals VoloXPro eVTOL for the Light-sport Aircraft Market

The VoloXPro will come to the market at a relatively low price compared to other eVTOL aircraft.

Cessna M2 Gen3 First Flight Advances Cert Program

Prototype will now enter expanded flight test phase

Textron Aviation Expands Wichita Flight-test Facility

Expansion was driven by SkyCourier and Denali programs

Honda Achieves First Full-scale eVTOL Flight

Remotely piloted aircraft completed 90-second flight in California

Textron Eyes CJ4 Gen3 FAA Cert as 500th CJ4 Rolls Out

Milestone aircraft is a Citation CJ4 Gen2

AIN Products

SUBSCRIPTIONS

RESOURCES

ABOUT AIN