Washington D.C. (including Baltimore) - Advance purchase of Amtrak tickets from BWI to DC

I'm planning a trip to DC with my 11-year-old for April. I can fly with points on SWA so we'lll be flying into BWI. I want to purchase Amtrak tickets from BWI to Union Station in advance, but I'm wondering what happens if our plane is delayed and we miss our train. Do I have to pay for tickets on a later train or can I just make an exchange? I looked on the Amtrak website and haven't been able to find the answer so far. Also, how much time should I allow for collecting our luggage and getting to the train station? Thanks!

If you're flying during the week when MARC trains are running, they would be cheaper than Amtrak and I think that MARC tickets are not for a particular train. There's no change fee for Amtrak, but there may be a fare difference.

This thread might be useful:

http://www.flyertalk.com/forum/amtrak-guest-rewards/827811-what-if-i-miss-my-train.html

Also, here is some info about the shuttle from BWI to the rail station:

http://www.bwiairport.com/en/travel/ground-transportation/trans/amtrak

i think all the trains on the nyc\dc line are now fully reserved. if you go to the amtrak site, type in refund in the search box.

Thanks for the help, everyone!

Phone Amtrak at 1-800-872-7245 to make sure. I recently purchased two tickets for Washington to Charlotte and was told by the Amtrak rep on the phone that if we didn't show up, our ticket would be automatically refunded (in the case of business class tickets, we'd have to cancel an hour in advance or lose something like 10%). If you miss the train on which you have reservations you should be able to buy a new ticket or, if the refund hasn't yet been made, change to another train at the BWI station (you might phone the main Amtrak number when you land).

According to http://mta.maryland.gov/sites/default/files/Pennlinefares.pdf, the fare from BWI to Washington Union Station on MARC commuter trains would be $6. Amtrak has fares as low as $11 (Acela high speed train costs $35).

MARC is cheaper than Amtrak but has two disadvantages: 1) it runs only on weekdays and even during the week has more limited hours than does Amtrak; 2) less space for luggage (it's aimed at commuters, who might have a briefcase or small backpack). It can also get crowded during rush hours, but I think the worst southbound would be in the morning, which I gather wouldn't affect you. For sample times, see http://mta.maryland.gov/sites/default/files/penn_Nov2011.pdf
It appears you'd want the Penn line (you'd get on at BWI Marshall stop; there's a free shuttle bus from the airport terminal to the train station). I believe for MARC you'd buy a ticket at the station (you may be able to buy on board, with an additional fee).

One other option is to take a Washington Metro bus from BWI to the Greenbelt Metro station and then Metro rail from there. See www.wmata.com. I've never used that.