An airplane boarding model, introduced earlier by Hemmer and Frette, is considered. In this model, N passengers have reserved seats, but enter the airplane in arbitrary order. Here we focus on the blocking relations between passengers. The total boarding time is equal to the longest blocking sequence, represented by a line, connecting points of the two-dimensional q versus r scatter plot. Here, \(q=i/N\) and \(r=j/N\), i and j being sequential numbers of passengers in the queue and their seat numbers, respectively. Such blocking sequences have been studied theoretically by Bachmat. We have developed an algorithm for numerical simulation of the longest blocking sequences, and have compared the results with analytical predictions for \(N \rightarrow \infty \).