Every major airline has been hit by a tech fiasco or two in the last several years, leading to severe delays, cancellations, and upset passengers. In the modern age, all of the systems at an airline need to talk to each other, and it’s not as simple as saying one is more important than another.

Passengers are quick to assume that the reservation system is the most important one, and it may well be the largest. But, there are other cogs in the wheel. While Southwest, Alaska, Virgin America, and Spirit fly one fleet of airplanes, they fly variations with different seating configurations. That means that if a Southwest 737-800 has to come out of service, it may not be possible to re-accommodate everyone on a smaller 737-700. Needless to say, at a company like United or Delta, it can be much more complex.

The reservation system also needs to communicate with the other systems in the network. While the airline can plan for a certain flight to be on a certain piece of equipment, there has to be some connection between, say, reservations and maintenance. When it comes to scheduling which airplane will be used on each flight, the maintenance schedule ultimately drives that decision.

Scheduled maintenance (certain inspections or periodically scheduled tasks) is the first consideration, followed by short-term unscheduled maintenance. For example, let’s say a 737 is scheduled to go in for a normal inspection at the end of the week. However, today the main cabin door has become difficult to open. The airline will try to rework the schedule to get the airplane to an airport (usually for an overnight stay) to get that door fixed—which may force the scheduled inspection back a few days because of modifications to the schedule.

Another wrinkle is a merger. Union contracts usually are specific about how a merger will work, including which pilots, flight attendants, and mechanics can touch which airplanes. All of this has to be programmed into the system. Further, airlines in a merger may fly the same airplane, but with vastly different seating and galley configurations.

From a pilot perspective, there is also the calculation of takeoff and landing performance data. The airlines use ACARS (Aircraft Crew and Reporting System), which is a communication network that connects the headquarters to the airplanes. ACARS has become a backbone upon which much of the day-to-day operation depends, and when it fails, it can bring things to a grinding halt. ACARS is the system by which performance data is transmitted to the airplane, and rarely is there a backup in place. It’s that reliable—until it isn’t.

These are just a few examples of the connectivity that takes place, but the gist is simple: It’s all tied together.

As a pilot, it’s critical that you understand all of the tools at your disposal, and just as important, you need to know what the back-up systems are and how to use them as efficiently as possible. Sometimes it’s as simple as a phone call, but sometimes it isn’t. Take notes and pay attention to what works and what doesn’t. And believe me when I say that the time will come when you find yourself wishing for the days of a simple POH and a couple of charts or graphs to determine if and when you can take off.—Chip Wright