if you make changes on or after Dec 15th, all change requests requiring a change to the “reward code” will be subject to the new revised mileage levels. For example, a change from economy to business class or a change from North America long-haul to Europe 1. For changes that consist of flight time, flight date or routing that do not include a change to the origin and destination or the reward code, mileage levels will remain the same. In the case of a mileage level decrease, changes will not be applied at the lower mileage levels.