I don't agree. There are around 145 flights a day between metro LA airports and metro SF airports (based on a quick Google Flights search for a random Friday).

I don't agree. There are around 145 flights a day between metro LA airports and metro SF airports (based on a quick Google Flights search for a random Friday). Assuming there's 75 seats on each plane, that's 10,000 seats a day. That's a lot of trains. A typical TGV is 500 seats. (If I add San Diego to SF, that's another 50 flights or 3,700 seats...) The market is there and exists, and that's with the gigantic hassle of having to get to and from the airports, as opposed to a convenient downtown train station Commuter rail is also a good idea but it's not the same thing as high speed rail. And commuter rail already exists: COASTER in San Diego, MetroLink in LA. Currently you either have an almost 11-hour trip on Amtrak, a 6 ½ hour drive, or a flight between LA and SF. The ridership is clearly there. (Believe it or not the Amtrak trains are often sold out.)