Short- and medium-range flights cause two thirds of current aircraft emissions

Roughly two-thirds of today’s kerosene consumption – which directly correlates with CO2 emissions – comes from flights operated with short- and medium-range aircraft (flights with fewer than 165 PAX and flights with fewer than 250 PAX, respectively). These aircraft account for 70 percent of the global fleet. Less than 5 percent of emissions are caused by regional (fewer than 80 PAX) and commuter (19 PAX or fewer) flights, which are served by about 20 percent of today’s aircraft. The remainder of emissions stem from long-range (over250 PAX) flights, which are served by 10 percent of aircraft.Regarding flight ranges, more than 20 percent of emissions come from flights above 7,000 kilometers, but these only make up less than 5 percent of the total number of flights. By contrast, flights spanning less than 3,000 kilometers and independent from the aircraft size account for more than 50 percent of total aviation CO2 emissions and 90 percent of all flights.This data indicates that the main focus on decarbonising aviation should be on short-range aircraft flying less than 2,000 to 3,000 kilometers, as well as on medium- and long-range aircraft.

The International Council on Clean Transportation in October 2020 offered a great insight into the challenges.

https://theicct.org/sites/default/files/publications/CO2-commercial-aviation-oct2020.pdf