Comment by ilamont

> The city center requires crossing a bridge.

It actually requires using tunnels or a boat. I used to drive a cab and the I93 + Callahan/Sumner tunnel route was hellish. The Big Dig helped a lot, although sometimes that can get pretty backed up too.

> Look at maps from 1950 and it doesn’t look like a bad location for a small airport.

Generally, airports that are close to major urban centers were developed prior to 1950, including all 3 examples named. Songshan was opened during Taiwan's colonial period as the “Matsuyama Airdrome” serving Japanese military flights (https://www.sups.tp.edu.tw/tsa/en/1-1.htm).

For bigger cities with these old central airports, larger airports were opened later in many cases. I don't think that will ever happen in Boston, although satellite airports in neighboring states like "Manchester-Boston" or TF Greene in Rhode Island try pretty hard.