Rigidbody.inertiaTensorRotation
var inertiaTensorRotation: Quaternion;
Quaternion inertiaTensorRotation;
inertiaTensorRotation as Quaternion
Description

The rotation of the inertia tensor.

If you don't set intertia tensor rotation from a script it will be calculated automatically from all colliders attached to the rigidbody.
	// Resets the inertia tensor to be the coordinate system of the transform

rigidbody.inertiaTensorRotation = Quaternion.identity;
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Example() {
        rigidbody.inertiaTensorRotation = Quaternion.identity;
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Example() as void:
		rigidbody.inertiaTensorRotation = Quaternion.identity