Perhaps the weirdest of New York’s vanished airports is the army airfield on Governors Island. Given that the only access (other than flying) is via ferry, the island isn’t a great place even for an army airport of any size, although there are things you can do with an airport without good access, like train pilots in era before a large-scale air force. The field was active for that purpose in the late 1910s and some, maybe most, of the 1920s.
To put this in some kind of order, it’s important to begin with the physical history of the island. Most of the land that exists now is fill, constructed in the between 1901 and 1910. (I think the work actually began later, but it’s a little hard to on down.) Here’s a piece of an 1781 map, with Manhattan at the top and “Brookland” on the lower right. Governors Island has its natural oval shape.
The landfill was, roughly, in the form of a long isosceles triangle with the original land on the short side. Or, as I always think of it, they added a cone below the ice cream. The fill material was largely excavation spoil from subway construction. Around the time that the fill work was being completed, in 1909, the Wright Brothers used the new land as a place to launch their flier (the picture at the top) for a demonstration flight around the harbor. So the first flight form the island took place before there was a real airfield there. Here’s an aerial photo for 1924, showing the landfill and the grass airfield in the middle, and the Red Hook docks in Brooklyn to the right:
The older section of the island is at the top, along with the buildings that make up the current historic district. The air field was a reasonable length, over 2000 feet long, but ultimately this was a bad place for training and not of great use for much else.
If you search around for this, you’ll see that the island was briefly discussed as a location for a commercial airport in the 1930s, before North Beach airport in Queens was expanded and converted to a municipal airport when LaGuardia was mayor. That idea was fatally flawed by the location (too close to downtown Manhattan and downtown Brooklyn for safety) and, again, the fact that the island is an island. A big bridge, or a new subway line, or filling in Buttermilk Channel would be necessary to get traffic to and from that theoretical airport, and that work would be more expensive to build than the airport itself.