It has clearly been shown that they could, which may be one of the reasons they sent the A320 in there.

The matter is under almost constant review, as with TTN-DEN, but it is a balance out. Frontier has been operating with a constrained fleet and the A319 seemed the most sensible plane to base there because no one actually knew what the reaction to TTN would be. As Frontier has said, they've had to sell the airport as much as the routes.

This is, for example, the first deep winter that the non-Florida routes have been flying and I'm surprised how well the loads are holding up.

Any new non-Florida route is a bit of a gamble - MSY and CMH didn't make the cut - as the new ones will be. I'm pretty confident about CLT - and even more so about BNA - but we wont actually know until they happen and I guess it possible that not all of them work.

Now there are strong rumours that they will assign a 4th aircraft there for the summer, but that becomes a balance out, too, partly because of the limited size of the terminal. Supposedly, baggage claim can presently only handle about one arriving A319 at a time - do they risk a greater crush by using the A320 or do they extend baggage claim?

One of the local newspapers described (positively) what is happening at TTN as "surreal" and I'd agree with that. I think it is one of the most interesting things happening in US civil aviation but it is very much a work in progress, constantly testing the limits of what the airport can handle.