What drives up the costs of air travel is fossil fuel -- whose prices define the future of almost every commodity in the market. A lucrative business, fossil fuel contributes greatly not only to markets but also to polluting the environment. Creating a sustainable air travel future requires alternative fuel ides -- and currently, innovators and scientists are looking into liquid hydrogen as the best solution against solar-powered air vehicles.

According to Science Blog, liquid hydrogen is feasibly but only for air travel. The blog cited physicist and Leiden University Professor Jo Hermans' work the "MRS Energy and Sustainability - A Review Journal" and his interview that said liquid hydrogen is the best air travel fuel for three reasons.

According to Hermans, liquid hydrogen -- deemed volatile -- could have liquid hydrogen trained experts to handle the process. He ascertains it can reduce liquid hydrogen dangers to "the same level of risk involved in handling kerosene." His second reason is that the light property of liquid hydrogen would save much fuel given airplanes will have further mileage.

According to NASA's blog, liquid hydrogen still remains the future choice for space travel fuel despite "early technical failures." The blog said the "taming of liquid hydrogen" has been achieved by the space agency. NASA said insulation was the key; liquid nitrogen needed protection from the Sun's heat, a catalyst for possible tank explosion.

Liquid nitrogen is already in use with space-related launches. NASA's blog indicates the space agency uses it as its "signature fuel" for launching satellites. It also mentioned that some advanced Boeing aircraft models such as Boeing Delta III and IV have liquid hydrogen and liquid oxygen advanced stages.

Hermans said solar power, which the public sees as the most viable option given aircraft could rise above clouds to absorb sunlight, will require the aircraft to undergo "revolutionary changes in the airplane concept," which can consequentially make air travel more expensive. Hermans also said liquid nitrogen is not the best option as a sustainable travel fuel for cars and land vehicles due to its high volatility -- offering instead electric-based technologies to power vehicles.