GGN420 got punted.
Even if there are flights and with all the years of posts I have never been convinced there are any really reliable ones in country, I think the hullaballoo required and the time needed take a flight vs. 4 hours on the bus at 1/20th the price (if that much) makes buses a more appropriate choice. Plus you get to see stuff and aren't risking your life on a Dominican only certified "airline".
Even here in Toronto the express train to Montreal (downtown to downtown) that takes a little less than 5 hours is really as fast as the sum of a 1 hour flight plus the time required to and from the airport, then waiting in checkin lines, security , boarding and delays, and has 1st class for the cost of coach air plus legroom and scenery. Same idea.