The Consumer Expenditure Survey (2007 data) shows (1, 2) that the higher a household’s income is, the more its members travel. Households whose income is above $150,000 a year spend on average about $4,000 a year on gasoline and motor oil, while household whose income is under $15,000 a year spend about $1,000.

The BLS groups air travel together with cruiseboat travel and mass transit under the heading “public transportation”. Most of the amount under this heading is spent on air travel, with the proportion increasing with income. The amount spent on “public transportation” is therefore a good indicator of the distance covered in travel by air, and inequalities in the expenditure in this category can serve as lower bounds for the inequalities in air travel. The expenditure within this category is overwhelmingly by the rich. The top 10% of households account for about half of the total expenditure on “public transportation” – a proportion similar to their share in the total income.