Passenger taxes are ineffective for reducing CO• 2 emissions. This is not just because demand is relatively price insensitive at a national and supra-national level. It is also because raising the cost of travel for the passenger does nothing to incentivise the manufacturer to produce new airframes or engines, nothing to incentivise the fuel company to produce a clean fuel, nothing to incentivise the EU to implement a Single European Sky, nothing to incentivise ANSPs to straighten routes and reduce stacking, nothing to incentivise airports to reduce taxiing emissions, and nothing to incentivise airlines to improve operations and renew their fleet.