Topic summary
IATA code

Extracted from the Wikipedia article International Air Transport Association code.
IATA codes are abbreviations that the International Air Transport Association (IATA) publishes to facilitate air travel. They are typically 1, 2, 3, or 4 character combinations (referred to as unigrams, digrams, trigrams, or tetragrams, respectively) that uniquely identify locations, equipment, companies, and times to standardize international flight operations. All codes within each group follow a pattern (same number of characters, and using either all letters or letter/digit combinations) to reduce the potential for error.