At the deceptive announcement of whose death did Yudhistra's chariot hitherto above the earth come down to earth ?

Yudhishthira's chariot, which had been floating above the ground due to his righteousness, came down to earth after he spoke the half-lie about Ashwattama's death. The deception was that Ashwattama the elephant was killed (not Ashwattama, Drona's son), but Yudhishthira let Drona believe it was his son. This intentional ambiguity in his words was the one major stain on his truthfulness, causing his chariot to lose its divine elevation.