sun+E asked:

I mean, the space shuttle Endeavor used fuel that was a mixture of oxygen and hydrogen, right?

Daniel asked:

ok part of this question has been answered thanks to Vincent G who’s answer to nomolino question helped me but i still want to know a it more. why do we rely on hydrogen fuel cells for the next generation of hydrogen cars? i know a big problem with electric for trucks is the power torque produced from electric motors is insufficient for large loads. i don’t see why we focus on converting chemical energy from hydrogen-oxygen reactions to to electrical energy, and then to kinetic through the already problematic electric motor when we could skip the electrical energy step.

The main problem of hydrogen is bulk, and second, its cryogenic nature — it need to be chilled to -252 C (-423 F) to be in liquid form.
First, the bulk issue. Liquid hydrogen takes about 4 times the volume of hydrocarbon fuel for the same amount of energy. Since long range airplane have fuel filling all of the wing, replacing jet fuel by hydrogen would mean filling the fulelage as well, leaving no room for the passenger or cargo, unless you are willing to have a much enlarged fuselage, or external tanks. But enlarged fuselage or external tanks would create more drag, so would need more powerfuel engines using more fuel. Hydrogen cars are easier to achieve because a car range is in the order of 300 to 400 km. Long range airplane can go 16000 km (about 9000 miles); and they need proportionally much more fuel than cars; up to half their maximum take off weight can be fuel.
Then you have the issue of the cold. A rocket can get by because it will remain in the atmosphere just a few minutes before reaching orbit — and even then, the insulation of the external tank of the space shuttle has proven problematic as we all know. But a long range airplane can be in the air for 14 hours or more, sometime flying in the rain and snow, imagine how much ice from condensation it would accumulate in the period. So thick insulation would be needed, adding even more to the bulk.
Companies ARE studying hydrogen fueled airplanes, but until a good solution to the above mentioned problems is found, they will remain purely in the research stage.