Germany's ruling conservatives have proposed doubling taxes on domestic flights, as part of a wider package to cut CO2 emissions.

The decision was taken by the leadership of the Christian Democrats (CDU), who form a coalition with the Christian Social Union (CSU) and the Social Democrats (SPD).

Tax of €7.38 (£6.5; $8.1) per ticket is currently levied on domestic flights.

Connecting flights that are part of long-haul journey will be exempt.

In its policy document (in German), the CDU also says that engines not powered by fossil fuels should be free of aviation tax.

"We will invest, together with the aviation industry, to make electric-powered flight standard for short-haul flights and to create synthetic fuel to achieve climate-neutrality on medium- and long-haul flights," the document says.

Travelling by plane has never been more popular, with four billion passengers around the world flying every year.

But aviation emissions contribute to climate change, and scientists say more needs to be done to tackle the problem.

Germany's governing coalition is expected to unveil a major climate package on 20 September.

It envisages more grants for electric car buyers, encouraging the usage of trains and raising road taxes for polluting vehicles.

However, reports say the coalition partners are still divided on how to finance the package which is believed to be costing several billions of euros per year initially.