1), possibly for extended periods of time, most often when weather conditions are less than optimal. This has motivated the development of numerical approaches to the problem of computing airport delays analytically. In another landmark paper, Koopman (1972) argued—and showed through examples drawn from New York’s Kennedy and LaGuardia Airports, at the time among the world’s busiest—that the queueing behavior of an airport with k “runway equivalents” (i.e., k nearly independent servers) can be bounded by the characteristics of the M(t)/M(t)/k and the M(t)/D(t)/k queueing models, each providing “worst-case” and “best-case” estimates, respectively.