Originally Posted by slowplay

Because the vans can depart from the hotel on a schedule. The airport not so much due to traffic and PANY/TSA shuttle parking rules.

I've used the Airtrain/shuttle from Federal Circle to get to the Marriott Courtyard van (just a few blocks away from our old one) when stuck in New York a few times. I'm not sure it's always quicker, but it definitely is more predictable.

The shuttle to the airport from our old hotel was an always late cattle car. I won't miss that hotel or the transportation.