Neither. In this case, “Chariot” (Hebrew: “Merkavah”) refers to a type of mysticism, kind of like proto-Kabbalah. In other words, he astrally ascended to heaven in a state of perfected consciousness, whilst his physical body probably just died normally. This is not dissimilar to the Yogic concept of “Mahasamadhi,” which is how great sages end their physical incarnation whilst in a state of perfected meditation.
Source: Alex Sumner’s answer to Was Elijah taken by God or aliens on a fiery chariot into heaven? – Quora