all the major US carriers have this kind of arrangement with regional airlines to fly to many of their destinations.
Yes but they all use jets. I haven’t flown a propeller plane on an affiliated airline (in this case Northwest Airlines) since mid-90s, and this was to Thief River Falls, not a city. Note that propeller planes fly at about 40% of the speed of an RJ.
The whole Aer Lingus experience was rinky-dink.
Could not select seats online either at time of purchase or once ticketed, had to call and wait (this is for a points ticket since it is issued by a third party, Avios.com).
A 7-3/4 hour transatlantic flight with NO ALCOHOL not even for purchase.
Could not get baggage tag printed for reservation with bag allowance, had to argue with staff and show itinerary.
10 minute bus ride to plane in Dublin, then another 10 minute bus ride in Birmingham. Sorry but this bus to plane is always rinky-dink, even if it happens in Amsterdam and Frankfurt also. (My only US experiences with bus to plane were at LaGuardia before it was remodeled).
On the BHX flight could not select a seat for free even after check in and water was for a fee. I’ve flown BA, KLM, and AF in Europe and always had meal/snack service and free beverage.