(REUTERS/Lucas Jackson)
This week, Delta Air Lines was forced to temporarily shut down flight operations after its computer system failed.
It took four days for the second largest airline in the world to recover from the disruption to its operation.
As a result, Delta was forced to cancel more than 2,000 flights while delaying thousands more.
Unfortunately, Delta is just the latest airline to suffer a catastrophic disruption to its service.
American, United, Southwest, and JetBlue have all been forced to temporarily ground its fleet in the past two years.
This leads us to ask the question — why do airlines suffer mass shutdowns?
"There are two kinds of mass cancellations – strategic and non-strategic," Phil Derner, NYC Aviation founder and FAA certified flight dispatcher, told Business Insider in an interview.
A strategic mass cancellation occurs when the airline has the opportunity to plan out the action. For instance, when an airline plans for an incoming hurricane or blizzard by completing certain flights to move its crew and aircraft out of harms way while cancelling others. A non-strategic mass cancellation happens suddenly and without warning.
"What happened to Delta this week was a non-strategic shutdown," Derner said.
So, what's is going on at an airline when a mass cancellation event does occur?
The daily operations of an airline is a neatly coordinated series of crew and aircraft movements. As an airline transports its customers, it's also strategically shifting its crew and equipment to various parts of the network.
(Delta Air Lines passengers at Tokyo Narita International Airport.AP)
As a result, when Delta's network was crippled by a computer outage this week, its crew and aircraft movement stopped along with the passenger traffic.
In statement this week, Delta wrote:
When Delta doesn’t fly aircraft, not only do customers not get to their destination, but flight crews don’t get to where they are scheduled to be. When this happens, unfortunately, further delays and cancellations result. And flight crews can only be on duty for a limited time before rest periods are required by law.
Flight crews – pilots and flight attendants – carry out their responsibilities in a rotation, a schedule of flights and hotel reservations, that is usually three or four days.
As cancellations occur, rotations become invalid. Multiplied across tens of thousands of pilots and flight attendants and thousands of scheduled flights, rebuilding rotations is a time-consuming process.
Airlines are in the business of making money. A flight cancellation could cost them tens of thousands of dollars. As a result, they prefer their planes to be up in the air generating revenue as much as possible. This means that the plane you are flying on is likely to have made as many as eight flights in one day depending on the duration of the trip. So if a plane gets grounded on its first flight of the day, there's a ripple effect down the line.