Independence Air was formally known as Atlantic Coast Airlines (ACA). Under the ACA banner, they flew as a regional airline for United and I believe Delta. Under United, they were more commonly known as United Express.
Their fleet currently consists of CRJ-200 regional jets but they have larger jets on order. If I recall, they are going to go with either the Airbus A319 or A320. The CRJ-200 generally holds up to 50 seats in a two by two seating configuration. By the way, carry on bags for the CRJ consist of rolling your bag out to the airplane and having it taken by the baggage loader. When you arrive at your destination, the bag is then waiting for you as you disembark from the airplane. Roll on's will not fit in the luggage compartment above because the space is too small. This is the process with United Express and every other carrier I've flown with that utilizes CRJ's so I assume Independence Air will follow suit. My one complaint on the CRJ-200 is the position of the passenger windows. They are somewhat lower than on most other aircraft and if you like to look out the window, you can expect a sore neck by the end of the flight! The CRJ-700 model has corrected this problem but Independence has no plans to fly them. The airplane is wonderful plane though and pilots love to fly them. On-board, you can expect to have 1 flight attendant unless Independence plans to add more. One should be plenty though as it does not take long to serve a drink and snack to 13 rows of people.
Dulles is their hub.
ACA terminated their relationship with United and branched out on it's own. Independence Air is the new name they chose.