Final answer:
For international flights, it is recommended to arrive at the airport two hours before departure to account for check-in, security, and boarding. Check-in and security can take significant time due to limited resources and heightened procedures, especially since the post-9/11 security changes. Boarding typically begins 30 to 60 minutes prior to departure.
Step-by-step explanation:
When preparing for international flights, travellers should be aware of several key timings related to their journey. Typically, it is recommended to arrive at the airport at least two hours prior to the scheduled departure time for international flights. This window allows passengers to check in, drop off any baggage, and obtain a boarding pass. Following check-in, passengers must proceed to security screening, which, as per the information provided, has become more intensive since the 9/11 hijackings.
After security, passengers will ​report to their gate, where it is common to wait in line to board the plane. Boarding generally begins 30 to 60 minutes before the flight's departure, although this can vary by airline and by airport. With the rate-determining step of limited ticket agents and security equipment, the time required for these processes can be significant, representing a major opportunity cost, as highlighted by the United States Department of Transportation.