Air Rights

Any NYC architect's office that does full buildings, or land use work. They could also advise on maximum building heights and FAR for the exiting lots. Google will be useless for this sort of thing -- you need to dig through ACRIS to find all the deed filings for the building you're interested in (and other adjacent properties as well, depending on how air rights may have been transferred around).

I did this for my apartment (with a kitchen lot line window), and found the air rights transfers myself, but had an architecture firm confirm my research, and reading of the deed texts (which were complicated, involving multiple lots), as well as advise me on potential heights of any new/revised buildings across the street.

Total cost was about $500, a meaningless fraction of the total cost, and well worth it to understand potential losses of windows / views.

Property Shark has a zoomable air rights map for NYC. Just zoom in to your building.

But it doesn't necessarily help, air rights are transferrable from one property to another.

http://www.propertyshark.com/mason/ny/New-York-City/Maps/Air-Rights

Thanks for the comments. The buildings I am looking at belong to a conglomerate that provides no infomation on the buildings I am seeking info on.
Arron2 - can you provide the name of the architecture firm you used. Thanks

Franke, Gottsegen, Cox, Architects
78 Union Street
Brooklyn, NY
(718) 596-3040
www.fgca.com