Owning a private jet is one of those far-fetched luxuries the average person can only dream about during a five-hour domestic flight cramped up in economy class. For the uber-wealthy, a private jet is not just a luxury, but it can also be a pretty lucrative business. Celebrities can enjoy traveling anywhere on a moment’s notice, and when they themselves aren’t in the air, they can rent the jet out for others to use. Experts estimate that an hour of flight time aboard a private jet introduces about two tonnes (also known as metric tons) of carbon dioxide into the...