Awesome pictures, look at that wing, the 777x is an amazing machine!
I think the regulatory hurdles discussed above (viewtopic.php?f=3&t=1455929&start=250#p22779375) come from the JATR report that came out a few years ago. It put the finger on extensive use of grandfathered design and requirements to save cost and time on essentially major changes. https://www.seattletimes.com/business/b ... -approval/ JATR consisted a broad group of (really independent) international aircraft certification experts and their more general observations and recommendations were taken over by international authorities. https://www.skybrary.aero/index.php/The ... view_(JATR)_-_Boeing_737_MAX_Flight_Control_System
While the 737MAX is clearly a derivative of the 737NG, but the 777X is essentially a new aircraft (new wings, engines, landing gear, fuselage, cockpit, systems, tail). Initial operation clearance for entry into service will be granted by local authorities of launching customers. This means extra review and even requirements. (No US customer / FAA approval). https://aviationnews.online/2019/11/29/ ... d-the-faa/
I think the 777-9 is more then foreseen required to meet the latest requirements, not requirements inherited form the 777-200 certification 26 years ago under the so called "Changed Product Rule". I think that as foreseen by few, denied & generalized by many, that took/takes a lot of time. viewtopic.php?t=1423759. EK's Clark is suggesting 2024-2025.
I think eventually the 777-9 will do great and I expect to see many on LHR, LAX and other long haul hubs for flight to/from Asia!