Do you think we will see a complete shift of European flights to HND then? The flights feeding them will have issues but the alternative is duplicate flights? Maybe a highspeed rail link under the bay between airports?
Wouldn't it be more reasonable and cheaper to connect NEX/Keikyu Airport lines to Haneda instead of building another line between Narita and Haneda? NEX already passes through Shinagawa so maybe just another split to Haneda Keikyu Airport line could in theory made to connect to Keisei main/Narita line so they can run express trains that way? Not sure how the timetables might look like hah. Many lines in Tokyo are starting to fuse or interconnect between different operators.
Hopefully that means we can get some red eye flights back from SFO to HND.