Question: Where is the headquarters where Hebert O. Fisher was an aviation executive? 

Context paragraphs:
Herbert O. Fisher: Herbert O. Fisher (March 6, 1909 – July 29, 1990) was an American test pilot and an aviation executive, overseeing aviation projects at the Port Authority of New York and New Jersey.  He worked for the Curtiss-Wright Corporation.  Fisher flew as a pilot for over 50 years, racking up 19,351 accident and violation free hours.

Linden Blue: Linden Stanley Blue (born 1936) is an American aviation executive.  He is the co-owner of General Atomics, where he serves as the Vice Chairman, and runs aircraft manufacturer Spectrum Aeronautical.

Gerald Gitner: Gerald L. "Gerry" Gitner is an American former aviation executive who occupied high-level positions at Trans World Airlines (TWA), Pan American World Airways (Pan Am), People Express Airlines, and other major airlines.  He has also served as chairman and director for several aviation-related and non-aviation-related companies.

James P. Wilmot: James P. Wilmot (1911–1980) was a pioneer aviation executive, landowner, philanthropist and horse breeder who served as Finance Chairman of the Democratic National Committee.  The James P. Wilmot Cancer Center at the University of Rochester is named in his honor.

Port Authority of New York and New Jersey: The Port Authority of New York and New Jersey (PANYNJ) is a joint venture between the U.S. states of New York and New Jersey, established in 1921 through an interstate compact authorized by the United States Congress.  The Port Authority oversees much of the regional transportation infrastructure, including bridges, tunnels, airports, and seaports, within the geographical jurisdiction of the Port of New York and New Jersey.  This 1,500 mi2 port district is generally encompassed within a 25 mi radius of the Statue of Liberty National Monument.  The Port Authority is headquartered at 4 World Trade Center and is a member of the Real Estate Board of New York.

Harvey Hancock: George Harvey Hancock (January 2, 1900 – January 8, 1996), known as Harvey Hancock, was an aviation executive and a journalist who served as the Northern California campaign manager for Richard Nixon's successful 1950 United States Senate race and then the 1952 general election won by Dwight D. Eisenhower and Nixon.

William Langhorne Bond: William Langhorne Bond (November 12, 1893- July 17, 1985) was an American aviator and aviation executive.  From 1931 until 1948 he was operations manager and vice-president of China National Aviation Corporation.

W. Paul Thayer: William Paul Thayer (November 23, 1919 – May 6, 2010) was a test pilot, aviation executive, and United States Deputy Secretary of Defense during the Reagan Administration.

William B. Robertson: Major William Bryan Robertson (October 8, 1893 –August 1, 1943) was an American aviator and aviation executive who was the co-founder of Lambert-St.  Louis Flying Field as well as the owner and President of Robertson Aircraft Corporation (RAC) located there, a company which he had co-founded with his brother, Frank, in 1918.

16th Aviation Brigade (Australia): The 16th Aviation Brigade (16 Avn Bde) commands all the Australian Army aviation units and has technical control of the Army Aviation Training Centre reporting to Forces Command.  The Brigade was formed on 2 April 2002 by combining Headquarters Divisional Aviation (Operational Command) and Headquarters Aviation Support Group (Technical Command) and is headquartered in Enoggera Barracks, Queensland.  It was originally named Headquarters 16th Brigade (Aviation) and was renamed to the 16th Aviation Brigade.

Supporting paragraphs: Herbert O. Fisher Port Authority of New York and New Jersey
Answer: 4 World Trade Center