Alan Gerber writes:

Underneath the New York Class B airspace: TEB (Teterboro), MMU
(Morristown), CDW (Caldwell), HPN (Westchester), and FRG (Farmingdale) -
all pretty busy Class D airports.

Underneath KPHX, Deer Valley, Scottsdale, Williams Gateway, Falcon
Field, Chandler. Scottsdale is very popular for GA, Williams handles
a lot of the overload from KPHX and is thus very busy for a Class D.

--
Transpose mxsmanic and gmail to reach me by e-mail.