Once the hydrogen economy is underway, air travel will be provided by a fleet of fuel-cell-powered dirigibles. A much greater than 80% CO2 reduction, sacrificing some speed but gaining (for the plebeian traveler) the replacement of discomfort by considerable comfort.
Shane Mage
"This cosmos did none of gods or men make, but it always was and is and shall be: an everlasting fire, kindling in measures and going out in measures."
Herakleitos of Ephesos, fr. 30