By Bjorn Fehrm

May 2, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.

We have since we started in October last year looked at:

• Alternative, lower emission, propulsion technologies, ranging from electric aircraft with batteries as energy source, different propulsion hybrids and new concepts for Jet-fuel and hydrogen gas turbine engines.
• We have also reviewed recent research on the role of CO2, NOx emissions, and Contrails generated by airliners.
• Last week, we summarized the present situation around SAF, Sustainable Aviation Fuel.

Before we proceed, we shall examine some facts about the scale of the emission/global warming influences from Air Transport.

Figure 1. A picture of global Air Transport flying different routes. Source: Flightradar24.

 Some data around Air Transport

When discussing the influence global Air Transport has on our climate and specifically the problem of global warming, and the actions we spend money on to mitigate these effects, it can be helpful to know some data around the issue:

• We presently have around 25,000 airliners that fly routes around the globe every day (Figure 1). The aircraft flies from one to two missions per day, typical for a dedicated Cargo aircraft, to the usual two missions per day for a long-haul widebody (one long and one short filler mission). The single-aisle airliner, which is usually used for domestic flights, flies around six to eight missions per day, with the regional airliners completing around the same number of sectors daily.
• The global Air Transport fleet consumes about 300 million tonnes of Jet-A1 fuel when flying these routes. As there is a mathematical direct relation between consumed fuel in a gas turbine engine and the generated CO2 (each kg of Jet fuel generates 3.16kg of CO2), we have a yearly emission from Air Transport of 950 million tonnes of CO2.
• On average, each active airliner consumes 12,000 tonnes of Jet fuel and generates 38,000 tonnes of CO2 annually.

The amount of Jet fuel consumed per passenger mile varies depending on the aircraft type that flies the route. For the present generation of aircraft, midsized and large aircraft are about twice as efficient per transported passenger as a 19-seat commuter aircraft.

For a 30 to 50-seat aircraft, we have a fuel consumption that is about 60% to 80% higher per transported passenger mile than the latest generation single-aisle aircraft like the Airbus A321neo or the forthcoming Boeing 737 MAX 10.

Once we reach the 70 to 80 seat turboprops, we talk about a 25% increase in fuel consumption per passenger mile, which is also valid for the 100 to 130 seat regional aircraft.

What does this all mean for reaching our emission goals

We shall use these numbers in the next Corners to put the investments and actions done so far to lower Air Transport Emissions into a more global and longer-term perspective.