747s are not flying any passengers in the US. They are flying passengers to the US. No US carrier still operates the queen of the skies, though that's mostly due to fuel efficiency. Some US carriers had the 747-400 until a couple years ago when United ditched their last one. I loved flying that bird! A few foreign carriers (Korean, Lufthansa) have the much newer 747-8i, which is a lovely plane but hasn't done well commercially due to those same fuel efficiency concerns.

But parent alleges that the 747 is outside of certification requirements, which is demonstrably false.

Neither United nor Delta retrofitted a fuel tank interting system, that's why they retired their 747s earlier than expected.

https://www.faa.gov/documentLibrary/media/Advisory_Circular/...

Paragraph 2-8 indicates the dates compliance became mandatory (Dec 26, 2017 with a potential one year extension). There are 747-400s flying in the United States, however they've all had interting systems retrofitted, are foreign registered, or both.