What is an aerodrome reference code?
An aerodrome reference code is a design classification, usually written as a number and a letter. It is not the passenger airport identifier on a baggage label, and it is not a universal permission for an aircraft to use a runway.
Two design elements
CAA CAP168, Table 3.1 and paragraphs 3.15–3.17, describes the number using aeroplane reference field length and the letter using wingspan. The code helps relate aerodrome design to the aircraft for which facilities are intended.
| Element | What it describes | What it does not identify |
|---|---|---|
| Number | Reference field-length category | The airport’s passenger code |
| Letter | Wingspan category | A unique airport or airline |
A worked example: 4C
| Element | CAP168 category |
|---|---|
| 4 | Aeroplane reference field length of 1,800 metres or more |
| C | Wingspan of at least 24 metres but less than 36 metres |
Read 4C as those two categories together. It does not say the physical runway is exactly 1,800 metres long, identify an airport, or provide the approved performance calculation for a particular flight.
Why a reference length is not the runway length
CAP168 explicitly separates selection of the code number from the actual runway length provided. It also says the reference code does not determine pavement strength. So a number-and-letter classification cannot, on its own, answer whether a particular aircraft operation is permitted or what take-off distance it needs.
That is why this explanation stops short of an operational calculator. Reading a design label is useful; treating it as aircraft-performance approval would answer a different question without the necessary information.
Do not confuse three kinds of code
STN and EGSS identify London Stansted in IATA and ICAO systems. An aerodrome reference code describes a design category instead. The words “airport code” can refer to different things in search results, so establish which system the document is discussing before comparing its labels.
For identifiers, use what an airport code is and the airport lookup. For the physical area the aircraft uses, read what a runway is. For technical requirements, consult the current applicable aerodrome standard rather than using this short explanation as design advice.
