Boeing gets FAA clearance to start 777X TIA Phase 4B testing, opening next stretch of certification work

Boeing Commercial Airplanes said the U.S. Federal Aviation Administration has cleared a key step in the certification-testing plan for the 777-9, the first model in the 777X family. The company disclosed the approval as Type Inspection Authorization (TIA) Phase 4B, a package of regulator-supervised flight and ground evaluations that Boeing uses to demonstrate compliance with U.S. airworthiness requirements.

TIA is the FAA authorization framework that typically follows a structured review of a manufacturer’s test-preparation package. Under the term “TIA,” the FAA authorizes official conformity, airworthiness inspections, and the ground and flight tests needed to meet type-certification requirements.

Boeing’s Commercial Airplanes President and CEO Stephanie Pope said the Phase 4B authorization unlocks the largest remaining portion of FAA-supervised flight testing work the company can execute. She described the step as enabling additional avionics and stability and control testing, plus human-factors flight testing. Pope also characterized 4B as the last TIA phase carrying a significant amount of work, with much of it focused on systems such as avionics.

Industry coverage of Pope’s remarks described Phase 4B as a demanding regulatory period in which FAA personnel directly participate in testing and help validate aircraft safety, checklists, and non-normal operations. The coverage also said Boeing expected the Phase 4B milestone to expand the company’s ability to continue moving through the certification process during the second half of 2026.

Boeing has previously broken the 777-9 TIA certification campaign into multiple stages. In Boeing’s first-quarter 2026 results, the company said the 777X program was progressing on certification and that the FAA had approved the start of the Type Inspection Authorization 4A phase of certification flight testing. In its fourth-quarter 2025 results, Boeing said the 777X program began the Type Inspection Authorization 3 phase of 777-9 certification flight testing and reiterated that it still anticipates first delivery in 2027.

Boeing did not provide in the disclosed remarks a detailed timetable for completing Phase 4B or a specific aircraft certification date. Pope did indicate, according to industry reporting, that TIA-4B flight testing on the 777X was not yet complete and that other phases of the TIA process represented much of the remaining work.

Still, the approval is a notable gating item for the 777-9, because it moves Boeing into a portion of the remaining certification work that is described as heavy on core systems evaluations under FAA oversight. Next to watch is whether Boeing reports progress completing the avionics, stability and control, and human-factors components of Phase 4B, and whether those updates align with Boeing’s continuing expectation for first delivery in 2027.