ploof-pack/faithless/assets/minecraft/models/block/air.json

{    "textures": {
        "particle": "block/air",
        "air": "#air"
    },
    "elements": [
        {   "from": [ 0, 0, 0 ],
            "to": [ 0, 0, 0 ],
            "shade": false,
            "faces": {
                "down": { "uv": [ 0, 0, 0, 0 ], "texture": "#air", "cullface": "down" }
            }
        }
    ]
}