Regular rail is already this, and for much of the Northeast is already roughly at or near time parity with flying, all things considered. If you have to arrive at the airport 2 hours early, and it takes 30 minutes-1 hour to leave by whatever means (renting a car, waiting for a bus or Uber, etc. + baggage return and simply walking through the airport), and then another 30 minutes-hour to actually arrive at your destination, arriving at your local station 10 minutes before departure and arriving in the city center/local destination station starts to look really attractive for flights of <2 hours/train rides of <6 hours.