What is not the case? 1-2% of total CO2 footprint? That flying a full plane is equivalent to months if not a year of driving a nontrivial distance every day?
I'm not saying cars are more efficient. It's just that the distance travelled is huge when one uses an airplane.
Many people use more fuel in a month getting to and from work than a round trip NYC to London flight. It comes down to both distance and fuel economy with some commuters putting in over 1000 miles a week. The range for commuting fuel uses vs transatlantic flight is much wider than 10x months to year.
I'm not saying cars are more efficient. It's just that the distance travelled is huge when one uses an airplane.