What type of performance is indicated by the numbers that identify jet fuels?

The identification numbers assigned to jet fuels are indeed designed to indicate types of fuel, but they do not directly correlate with the performance characteristics of the fuels. These type numbers help categorize and standardize fuels based on their composition and operational properties rather than quantifying their performance in terms of efficiency, thrust, or emissions.

Each type of jet fuel, such as Jet A or Jet A-1, is formulated to meet specific requirements, and while the type numbers provide important information about their intended use, they do not measure or indicate the actual performance metrics such as fuel efficiency or emissions output. Therefore, the choice correctly suggests that the numbers are primarily related to classifications rather than direct performance indicators.

This context helps clarify how jet fuel types are organized and the significance of their designations within aviation operations.