Why the aviation fuel is more harmful to the environment than others?

Falling ticket prices and rising incomes are leading to rapid growth in global air travel. According to the British government, the number of British air passengers will more than double in the next quarter of a century. Increases of such an order would mean much more aviation fuel being burned and aviation fuel may be more harmful to the environment than other fuels because the resulting smoke is emitted at high altitudes.
     The British government wants the use of aviation fuel covered by international agreement on the environment. The difficulty for any individual government is that taxing fuel used at its own airports might push airlines to move their operations to competing airports in other countries.