Procedure

(1) Digital recordings of Toronto Centre air traffic control were downloaded.

(2) A classification system was developed for each type of flight: C (Canadian airline), I (international airline), U (U.S. Airline), O (other, e.g. medical evacuation, private plane, military, traffic helicopter, etc.)

(3) A classification system was developed
for each type of readback: C (correct),
I (incorrect), M (missed), S (“say again”).

(4) A spreadsheet was designed with three columns: Tape ID, Type of Flight, and Type of Readback.

(5) Approximately 1,000 calls were listened to, over a period of about five hours. Entries were made for 353 of these calls (only complete transmissions and readbacks were considered).

(6) The data in the spreadsheet was analyzed and graphs were made to show the results and support the conclusion.