I am trying to figure out what is the maximum sized bag that I can carry on to a regional jet (embraer, etc.)?
Is there more space under the seats or in the overhead bins?
Is there a maximum size that will fit as the 22 x 14 x 9 does for bigger planes?
Can a person take on 2 bags, one small enough to fit in the overhead, and one small enough to fit under the seat, or if you have two bags, you will always be asked to gate check one?
The best regional jets for carry-on luggage are the Embraer family of 170, 175, 190 and 195 models. These aircrafts have overhead bins that could handle standard 22x14x9 roll-aboard cases. For other regional jets, I recommend traveling with soft-side bags so that they can be made to fit the irregular shaped space of the overhead bin. One of our staff has a back-pack type soft case with wheels, measuring only 19x13x7, and he still has trouble getting it into regional jet overhead bins, and typically had to place it under the seat in front of his legs.
As for bring on two bags, as long as they are small enough, I do not believe you will be forced to gate check them.