London Heathrow airport called on the U.K. to mandate the use of sustainable aviation fuels to help the industry lower carbon emissions while fending off pressure from climate groups to curtail air travel.

The hub is also seeking other policies that would scale up the production of SAF in the country, including a price-support mechanism and loan guarantees, according to a statement Monday.

The demand comes as debate intensifies over how to tackle the challenge of lowering air travel’s carbon footprint—and who pays for it. Last week, the airline industry’s main lobby group adopted a target of eliminating carbon emissions on a net basis by 2050.

Increasingly, the industry has rallied around SAF—which the latest jets can easily accommodate—as one way to cut back on the use of conventional fuel. However, it is expensive and still produced in only limited amounts. Without uniform rules, carriers that push ahead with the technology will be at an economic disadvantage.

“We should aim for 2019 to have been the peak year for fossil-fuel use in global aviation,” Heathrow Chief Executive Officer John Holland-Kaye said in the statement.

Heathrow is seeking a mechanism called contracts for difference to support SAF prices. CFDs, used now in the renewable energy industry, establish a fixed price for generation over a period of time. This provides suppliers with certainty on future revenue, helping them secure financing. If the market level is below the so-called strike price, the producer receives a top-up from the U.K. taxpayer. If it is higher, the producer pays back the difference.

Set Example

Holland-Kaye called on the U.K. to set an example as it hosts the coming COP26 climate conference at the end of this month, and said an acceleration of SAF use “will protect the benefits of flying for future generations.”

Before the coronavirus pandemic, the global aviation industry caused about 2% of all CO2 emissions, though the sharp drop resulting from the outbreak is likely to be temporary. Airlines which borrowed heavily and have been selling stock to weather the downturn are now under pressure to return to previous levels of flying.

While breakthrough technology like hydrogen-powered planes remain years away, climate groups across Europe have sought bans on short flights and asked for them to be replaced by rail journeys.

The Campaign for Better Transport charity asked the U.K. to ban internal flights if an equivalent train journey took less than five hours, the Guardian newspaper reported, citing an interview with CBT chief executive officer Paul Tuohy. He also urged the government to resist calls for any cut in air passenger duty.

The U.K. began a consultation on the reduction or elimination of air-passenger duty on domestic flights to spur regional connectivity during the pandemic. A final decision is expected soon.