The sky got very crowded last year with over 3 billion people travelling by air, according to preliminary figures from the International Civil Aviation Organization (ICAO). The world's 3 billion travelers took off on 33 million fights, beating the previous year's total by a million.
But with extra trips come extra carbon emissions.
In the Netherlands, one of the world's biggest airlines, KLM, is attempting to lessen the environmental impact of air travel by investing in ideas that could help aircraft fly using biofuels alongside conventional fossil fuels.
In May 2014 the airline launched a series of transatlantic flights from Amsterdam to Aruba and Bonaire. During these flights, an Airbus A330-200 was powered by a mixture of fossil fuels and sustainable biofuel.
"We started in May, and we started two series of 10 biofuel flights on a weekly basis," Inka Pieter, Director of Corporate Social Responsibility & Environmental Strategy at KLM, told CNBC's Sustainable Energy.
KLM's biofuel planes use a truck to refuel. "With this truck, I fill the plane with a blend of biofuel and fossil fuel," Leo Drost, a Fuel Operator for KLM, said.
"My colleague on the other side of the plane is standing on the dispenser. He will fill the left side of the plane only with fossil fuel," Drost added. When the plane is airborne, the fuels are mixed and burnt normally.
The original source of KLM's biofuels may shock some travellers, but it is aviation grade and safe to use on flights. "The sustainable biofuel we use is made from various feedstocks," Eileen van den Tweel, Manager, Innovation, at KLM told CNBC.
"We use used cooking oil and Camelina oil," van den Tweel added. "In the future there will be different types of feedstock that we will be using."
The use of biofuels reflects KLM's wider green goals, which include a 20 percent cut in CO2 emissions by 2020, when compared with 2009.
Is cost an issue? "At present, costs related to bio fuel are three to four times those of normal kerosene. Despite facing financial challenges and limited feedstock, KLM will continue to pursue this strategy," a spokesperson for KLM told CNBC.com.
Across aviation as a whole, a concerted effort to "go green" seems to be taking place. According to the International Air Transport Association (IATA), airlines have set themselves a voluntary target to, "reduce fuel consumption and CO2 emissions (per revenue tonne kilometer), by at least 25 percent by 2020, compared to 2005 levels."
Reassuringly, the pilots flying the planes see no difference between the two fuel types.
"We don't see any difference between biofuel and normal fuel, there's no difference in their performance, there's no difference in our indicators," Eimerd Bult, Captain and Operations Manager at KLM, told CNBC. "The spec for normal fuel and biofuel are exactly the same," Bult added.