An illustration of what the new airport in Mexico City might look like when it is completed.

The airport of the future will be less like a sprawling bus depot and more like a large, sustainable park.

The number of passengers and aircraft are set to double by 2033, according to Jack Plunkett, CEO of Plunkett Research, a firm specializing in the travel industry. To adapt to the growing crowds, airports are changing, and a select few are prioritizing sustainability as part of the process.

"You could sum up the future of airports in one simple phrase, and that is: Much bigger, and much more efficient," said Plunkett.

Right now a new airport is being built in Mexico City, which is slated for completion by 2020 and will make traveling better for passengers and the environment.

The airport is expected to service 50 million people a year and the new design is all about energy efficiency. Gates will be within walking distance, and the roof is being built to incorporate solar technology. There will also be an on-site energy plant that will collect, treat and recycle rainwater.