Beijing Capital International Airport, in Beijing, China.

What is the difference between PEK and ZBAA?

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

Is PEK the same as PKX?

No. PKX is daxing, Beijing's second and newer mega-airport, 46 km south of the city.

What airport is PEK?

PEK is

Beijing Capital International Airport

Beijing, China

Why the code is PEK

PEKing, the older romanisation of Beijing.

The airport authority or a contemporaneous record states this directly.

The airport

IATA code: PEK
ICAO code: ZBAA
Airport: Beijing Capital International Airport
City: Beijing, China
Code origin: Documented

The code preserves Peking, the Wade-Giles form abandoned for Beijing in the 1970s, because changing an IATA code is disruptive enough that airports almost never do it. The same conservatism is why Mumbai is BOM and Chennai is MAA.

Codes people book by mistake

Code	What it actually is
PKX	Daxing, Beijing's second and newer mega-airport, 46 km south of the city.

The other code, ZBAA

Every airport has two codes. The three-letter IATA code, PEK, is the one on your boarding pass and your luggage tag, and it is assigned for commercial use. The four-letter ICAO code, ZBAA, 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 ZBAA looks nothing like PEK.

Common questions

What airport is PEK?: Beijing Capital International Airport, in Beijing, China.
Why is Beijing's airport called PEK?: PEKing, the older romanisation of Beijing.
What is the difference between PEK and ZBAA?: PEK is the IATA code, used commercially — tickets, timetables, luggage tags. ZBAA is the ICAO code, used operationally by pilots and air traffic control, and assigned geographically by region.
Is PEK the same as PKX?: No. PKX is daxing, Beijing's second and newer mega-airport, 46 km south of the city.

China Capital, area, population and currency
The flag of China Colours, symbols and lookalikes
Airport codes in China 3 here
What airport is PKX? Beijing Daxing International Airport
What airport is PVG? Shanghai Pudong International Airport, Shanghai
What airport is PKX? Beijing Daxing International Airport, Beijing

Sources

OurAirports — OurAirports (Public domain)

How these figures are compiled and checked