taxes, paid by airlines for the consumed jet fuel, like the kerosene tax for the European Union or fuel taxes in the United States. Consumer behavior can be influenced by cutting subsidies for unsustainable aviation and subsidising the development of sustainable alternatives. By September–October 2019, a carbon tax on flights would be supported by 72% of the EU citizens, in a poll conducted for the European Investment Bank. Aviation taxation could reflect all its external costs and could be included in an emissions trading scheme. International aviation emissions escaped international regulation until the ICAO triennial conference in 2016 agreed on the CORSIA offset scheme. Due to low or nonexistent taxes on aviation fuel, air travel has a competitive advantage over other transportation modes. Carbon offsetting A carbon offset is a means of compensating aviation emissions by saving enough carbon or absorbing carbon back into plants through photosynthesis (for example, by planting trees through reforestation or afforestation) to balance the carbon emitted by a particular action. However, carbon credits permanence and additionality can be questionnable. More than 90% of rainforest offset credits certified by Verra's Verified Carbon Standard may not represent genuine carbon reductions. Consumer option Some airlines offer carbon offsets to passengers to cover the emissions created by their flight, invested in green technology such as renewable energy and research into future technology. Airlines offering carbon offsets include British Airways, Continental Airlines, easyJet,; and also Air Canada, Air New Zealand, Delta Air Lines, Emirates Airlines, Gulf Air, Jetstar, Lufthansa, Qantas, United Airlines and Virgin Australia. Consumers can also purchase offsets on the individual market. There are certification standards for these, including the Gold Standard and the Green-e. National carbon budgets In UK, transportation replaced power generation as the largest emissions source. This includes aviation's 4% contribution. This is expected to expand until 2050 and passenger demand may need to be reduced. For the UK Committee on Climate Change (CCC), the UK target of an 80% reduction from 1990 to 2050 was still achievable from 2019, but the committee suggests that the Paris Agreement should tighten its emission targets. Their position is that emissions in problematic sectors, like aviation, should be offset by greenhouse gas removal, carbon capture and storage and reforestation. The UK will include international aviation and shipping in their carbon budgets and hopes other countries will too. Airline offsets Some airlines have been carbon-neutral like Costa Rican Nature