LATAM is the new symbol of national airlines of Chile, before LAN ( Today Latin America 41 air lines are called; after buying other airlines, like for example Aires in Colombia.
Is likely that is concerned of an abbreviation in English of the word Latinamerica or latinamerican. The habit of shortening words is characteristic of this language.
Corresponds to various issues. On the one hand, are the acronyms of a company of airline Chilean, LATAM, that data of the year 1929. And on the other hand, as Manuel Penichet, says it is an abbreviation that refers to the Latin American.