Learn Spanish (Latin America): El vuelo va directamente a México.

Adverbs ending in -mente (which is like "-ly" in English) are built from the feminine form of the adjective. The adjective for "direct" is directo, so we take the feminine form directa and add -mente to get directamente (directly).

Is it possible to just use directo instead of directamente?

Yes! In everyday Spanish, it is very common to hear El vuelo va directo a México. Using the masculine singular adjective as an adverb is a spoken shortcut native speakers often take, but directamente is the grammatically complete, standard way to say "directly".

Why do we need the word a before México?

The verb ir (which gives us va, meaning "goes") is a verb of motion. In Spanish, when you are moving toward a specific destination, you almost always use the preposition a (to) to connect the motion to the place you are going.

Why is the "x" in México pronounced like an English "h"?