The boss of Hungarian budget airline Wizz Air has attacked the sustainability credentials of traditional airlines like Air France-KLM and Lufthansa, saying business class flying was bad for the environment.

The carbon emissions of airlines has been thrown into the spotlight since travel restarted after Covid and as worries over climate change grow.

Wizz Air's chief executive Jozsef Varadi told the CAPA industry conference online that there was no place for business class on short-haul flights.

"Why do we have to fly business class, especially on short haul? A business passenger occupies a lot more space therefore the environmental footprint of your passenger is much greater," he said today.

The comments came as world leaders gathered today at the COP26 climate conference in Glasgow, where a number of announcements related to the greening of transportation were expected.

They also opened a new front in the battle between newer low-cost carriers and older more traditional airlines over tackling the environmental burden.

Legacy airline leaders including Lufthansa's boss Carsten Spohr have criticised low-cost carriers for offering what they describe as unrealistically low fares to stimulate travel at the expense of the environment.

Budget airlines like Wizz only offer one class of flying, while full-service airlines like Lufthansa offer different classes with more space for those willing to pay more.

Varadi said sustainability meant change in future: "I think that will require some of the airlines to fundamentally rethink how they are doing business and their business approach."

British low cost airline EasyJet said it planned to present further details of its net-zero roadmap in the coming months after committing to reach net-zero emissions by 2050.

Aer Lingus and British Airways-owner IAG said today it agreed to purchase 220,000 tonnes of sustainable aviation fuel (SAF) from Velocys over 10 years, as part of its goal of using 10% SAF by 2030.

The SAF will be used by IAG airlines including British Airways, Aer Lingus and Iberia.

It said the technology used in this project will capture CO2 from the manufacturing process to permanently remove it from the atmosphere.

IAG was the first European airline group to commit to powering 10% of its flights with sustainable aviation fuel by 2030.

The group said it will purchase one million tonnes of sustainable jet fuel per year enabling it to cut its annual emissions by two million tonnes by 2030. It said this equates to removing one million cars from Europe's roads each year.

Luis Gallego, CEO of IAG

Luis Gallego, IAG's chief executive, said that sustainable aviation fuel is a critical element for the decarbonisation of the aviation industry.

"Clear policy support is needed to attract investment to construct the necessary plants to deliver enough supply for the airline industry. This project has benefitted from strong policy support from the US, creating highly valued green jobs and economic growth," the IAG boss said.

"We would encourage the UK and the EU to follow suit in supporting the development and deployment of green technologies including carbon capture," he added.