Tokyo Haneda Airport, in Tokyo, Japan.

What is the difference between HND and RJTT?

HND is the IATA code, used commercially — tickets, timetables, luggage tags. RJTT is the ICAO code, used operationally by pilots and air traffic control, and assigned geographically by region.

Is HND the same as NRT?

No. NRT is narita, an hour further out. TYO covers both, and booking the wrong one costs a two-hour transfer.

What airport is HND?

HND is

Tokyo Haneda Airport

Tokyo, Japan

Why the code is HND

HaNeDa, the district it sits in.

The airport authority or a contemporaneous record states this directly.

The airport

IATA code: HND
ICAO code: RJTT
Airport: Tokyo Haneda Airport
City: Tokyo, Japan
Opened: 1931
Code origin: Documented

Haneda is 14 km from central Tokyo against Narita's 60 km, and international flights were largely moved away from it in 1978 and then gradually moved back from 2010 — so the "which Tokyo airport" question has had three different right answers in fifty years. It is consistently ranked among the most punctual large airports in the world.

Codes people book by mistake

Code	What it actually is
NRT	Narita, an hour further out. TYO covers both, and booking the wrong one costs a two-hour transfer.

The other code, RJTT

Every airport has two codes. The three-letter IATA code, HND, is the one on your boarding pass and your luggage tag, and it is assigned for commercial use. The four-letter ICAO code, RJTT, is the one pilots and controllers use, and it is assigned geographically: the first letter or two identify the region, so every airport in the same part of the world shares a prefix. That is why RJTT looks nothing like HND.

Common questions

What airport is HND?: Tokyo Haneda Airport, in Tokyo, Japan.
Why is Tokyo's airport called HND?: HaNeDa, the district it sits in.
What is the difference between HND and RJTT?: HND is the IATA code, used commercially — tickets, timetables, luggage tags. RJTT is the ICAO code, used operationally by pilots and air traffic control, and assigned geographically by region.
Is HND the same as NRT?: No. NRT is narita, an hour further out. TYO covers both, and booking the wrong one costs a two-hour transfer.

Japan Capital, area, population and currency
The flag of Japan Colours, symbols and lookalikes
Airport codes in Japan 3 here
What airport is NRT? Narita International Airport
What airport is NRT? Narita International Airport, Tokyo
What airport is KIX? Kansai International Airport, Osaka

Sources

OurAirports — OurAirports (Public domain)

How these figures are compiled and checked