Climate One: Will Sustainable Aviation Ever Take Off?

For those of us who love to travel, climate guilt weighs heavily. Civil aviation accounts for about 3% of global greenhouse gas emissions, and that number is going up. But while electrifying cars and trucks is already well underway, flying planes on anything other than liquid fuels remains devilishly difficult. Despite that difficulty, there are options. But how sustainable are the options, and are they really ready for prime time?