IATA airport codes are often based on the first three letters of the airport's city. For example, ATL is the location identifier for the Hartsfield-Jackson Atlanta International Airport, and MEX is used for Mexico City. The airport codes can also refer to the city's initials–HKG for Hong Kong or SLC for Salt Lake City.
Pilots are instructed to land at the nearest possible suitable airport in the event of a Code Red. Hearing Code Red at the terminal typically means there's a confirmed security risk, such as a bomb or terrorist. Airport security and police are almost immediately mobilized to deal with the situation.
With the rapid growth in the aviation industry, in 1947, the identifiers expanded to three letters and LA received an extra letter to become LAX. The letter X does not otherwise have any specific meaning in this identifier.
Saudi Arabia's King Fahr International Airport covered by far the largest land area, more than ten times the size of the third biggest airport in the ranking, Dallas/Fort Worth International in the United States.
Threshold lights are green color airfield lights, unidirectional type, installed at the beginning of the part of a runway where aircraft can do touchdown. Threshold is not a touchdown point yet. But this is a beginning of 'safe-to-land' part of a runway.
One of the most well-known is a 'Code Bravo,' which means that there has been a security breach/threat. In airports, security staff may issue the call 'Bravo, Bravo, Bravo' and order everyone to freeze, to help them identify a suspect.