It's really hard to decipher whether the delay is a redesign issue, more scrutiny in certification or just a flat out lack of demand for VLA aircraft with full recovery not expected until 2025 if ever.
Let me put this way. More scrutiny is causing a redesign and that is line with demand anyway. Demand is not the major driver here even though there isn’t much because had the plane been ready Boeing would’ve forced some deliveries due to contract agreement.
Is this Boeing or 777X specific or will all future programs take 4 or 5 years of flight testing? If this is the new norm it might make launching future aircraft more prohibitive. Which systems are requiring a redesign?
I'm not sure why you say this is an issue of flight test duration.
The bulk of what we know is in #189 above: viewtopic.php?t=1455929&start=150#p22636013
This was in January of this year, and shortly thereafter the slip was announced.
There are several articles on this, here's a snip from one that gives the CEO's statements:
Boeing has revised its development schedule for the 777X to reflect a late 2023 first delivery and resumption of shipments of the 787 Dreamliner late in the first quarter as the company’s widebody programs continue to address technical snags and market softness. Speaking Wednesday during the company’s fourth-quarter 2020 earnings call, Boeing CEO David Calhoun explained that the 777X delay centers on three main factors, leading with an updated assessment of global certification requirements influenced by the 737 Max grounding.
“We’re working closely with global regulators on all aspects of 777X development,” said Calhoun. “This involves listening to all their feedback and applying lessons learned from our experiences on the 737 Max program recertification and applying it to our 777 certification plans. It also involves making prudent design modifications as necessary to meet the various global regulators' expectations.”
As part of its assessment, Boeing decided to make “certain modifications” to the aircraft design involving both software and hardware changes to the actuator control electronics, he explained, reflecting the company’s “current judgment of global regulators compliance expectations.”
Ref: https://www.ainonline.com/aviation-news ... -late-2023
He goes on to give the other two factors, the covid crisis reducing the demand for long haul aircraft and the airline's requests to defer deliveries.
I think the "current judgment of global regulators compliance expectations" suggests frustration on getting the regulator to clearly communicate their desires, but given they are still working through the aftermath of the MCAS crisis, they have no choice but to wait things out, even if this means waiting till late 2023 or beyond for first delivery.
I think it's fair to say that a lot of this is due to the fact that the regulators are naturally going to heavily scrutinize Boeing in the aftermath of the MCAS tragedy.