That's a bad comparison. Generally, shrinking the size of a packaged good is a way to compensate for inflation without sticker shock, a huge problem in a very price-sensitive market like groceries. The chief the government measures inflation, in fact, is the Consumer Price Index, which measures the cost of a "basket" of consumer goods. [0]

The cost of flying, on the other hand, has fallen dramatically since deregulation. [1]

[0] https://www.bls.gov/CPI/ [1] https://www.theatlantic.com/business/archive/2013/02/how-air...