The biggest hurdle however, is the fact that unlike other sectors, there are not many eco-friendly alternatives for civil aviation to transport 10m passengers per day
. Today, efforts are focused on making airplanes more fuel-efficient by reducing weight or optimizing operations, such as reducing wait time in the air or optimizing flight routes. New technologies like electrical airplanes are being worked on, however they will require a few more decades
before they become operational. Indeed, they would require batteries, whose energy density is currently 50 times lower
than that of liquid fuels. In addition, airplanes consume fuel during the flight, making them lighter and more efficient throughout the journey. This puts an even bigger constraint on electrical airplanes, which have to carry heavy batteries during the entire flight time.