In the 1990s, I recall that the DC-NY-Boston Shuttles were popular; regular mainline planes (although with "Shuttle Class" seating) were used on US Airways, and I believe that US Airways promised that if a flight was full, it would roll out an additional plane, even for just one passenger. Flights seemed to be every hour.

Now, flights are on regional jets and there are large blocks of time when there are no Shuttle flights.

What gives? Has Amtrak just gained a lot of market share due to the Acela? Is the Shuttle not profitable?

It would be great if AA and Amtrak would have a code-sharing arrangement; for example, there is a 3-hour gap on Saturday afternoon when there are no Shuttle flights from Washington to NY, so I'd prefer to just take the Acela instead of waiting in the airport (due to a layover).

Thanks.