Did you know that 50% of fuel used during a standard flight is burned during take-off and landing, for which weight is a major contributing factor? The weight of the plane therefore directly affects the emissions of the flight, which means how much you pack has a real impact. Nonetheless airline companies often offer only no checked in luggage, or 20 kgs. One then feels they should get their money's worth and use up that weight allowance! This should be changed to a pay-as-you-need type system. Airlines should also offer incentives like cheaper tickets and frequent flyer points when passengers travel light. The knock-on changes to our behaviour could make a real difference.