Go to plane section ( check my tuto youtube) and replace files just after :

"biplane": {
        "type": "plane",
        "soundType": "plane",
        "objectModel": "biplane",
        "weaponType": "none",
        "propellerModel": "biplaneprop",
        "accelMultiplier": 0.08,
        "propellerOffsets": { "x": 0.0, "y": 2.6, "z": 1.1, "rx": 0.0, "ry": 0.0, "rz": 0.0 },
        "attachOffsets": [-0.0, 1.2, 1.0, 0.0, 0.0, 0.0],
        "cloneOffsets": { "x": -0.0, "y": -0.65, "z": 0.5, "rx": 0.0, "ry": 0.0, "rz": 0.0 },
        "ThirdPersonCamDistances": [10.0, 14.0, 18.0]
    },

    it should look like this :

"       biplane": {
        "type": "plane",
        "soundType": "plane",
        "objectModel": "biplane",
        "weaponType": "none",
        "propellerModel": "biplaneprop",
        "accelMultiplier": 0.08,
        "propellerOffsets": { "x": 0.0, "y": 2.6, "z": 1.1, "rx": 0.0, "ry": 0.0, "rz": 0.0 },
        "attachOffsets": [-0.0, 1.2, 1.0, 0.0, 0.0, 0.0],
        "cloneOffsets": { "x": -0.0, "y": -0.65, "z": 0.5, "rx": 0.0, "ry": 0.0, "rz": 0.0 },
        "ThirdPersonCamDistances": [10.0, 14.0, 18.0]
    },
        "Santas_Sleigh_christmas": {
        "type": "plane",
        "soundType": "plane",
        "objectModel": "traineau",
        "weaponType": "none",
        "propellerModel": "sucreorge",
        "accelMultiplier": 0.06,
        "propellerOffsets": { "x": 0.0, "y": -2.2, "z": 0.7, "rx": 0.0, "ry": 0.0, "rz": 0.0 },
        "attachOffsets": [-0.0, 1.2, 1.0, 0.0, 0.0, 0.0],
        "cloneOffsets": { "x": 0.2, "y": -1.60, "z": -0.15, "rx": 0.0, "ry": 0.0, "rz": 0.0 },
        "ThirdPersonCamDistances": [10.0, 14.0, 18.0]
    },


its OKAY.