Why some flights are delayed and some flights are on time

Airlines ultimately control issues determining what flights leave on time and what flights are delayed

what flights leave on-timeMany travelers don’t realize that all flights are not equally likely to be delayed or leave on time. And, while the algorithm may not be apparent to anyone who isn’t working for the airlines involved, it’s usually not random chance which flights are most affected.

Sometimes it’s weather, at other times air traffic control issues… At the time of writing it’s a major runway closure at San Francisco Airport. The result is fewer than normal flights can take off and land, and many flights end up delayed or canceled.

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If an airport is closed, that’s one thing. But when it’s operating at temporarily reduced capacity, for any reason, airlines are likely to be told how many flights they can have take off and land within a given time. The airlines then can decide accordingly what flights leave on-time and what flights are delayed.

What flights leave on time?

The simple explanation that the deciding factor is money determines, in my experience, the flights that airlines ultimately decide to prioritize.

  1. International flights. These flights are high revenue destinations for more than one reason. They usually carry paying premier class passengers, and they also carry cargo.  Both of which are valuable to an airline’s bottom line. And they tend to be routes that are both longer flights and that operate once or twice a day at most. It’s nontrivial to cancel them. Also, because of crew flight time restrictions, delaying an international flight might mean needing a new crew, which can cause further delays and expense.
  2. Infrequent long haul flights. Hawaii is a major example. When an airline has few options for passengers who want to switch flights, or for that matter to get new crews if a delay causes a crew to time out, then the airline will want to get those flights in the air. (Sometimes to Hawaii the same crew may go with a plane across the Pacific both ways, in which case the margin for error is small.)
  3. Early morning flights. Delays snowball, so if an airline can get a plane in the air as soon as possible, it reduces the number of delays further into the afternoon and evening.

What flights are delayed

  1. Short flights. Especially later in the day, an airline will cancel some short flights. This will happen particularly if flights are frequent. Airlines then combine passengers onto earlier or later flights.
  2. Flights from smaller airports. Los Angeles to San Francisco (SFO) flights have some cancellations and various levels of delays. But flights from Burbank to SFO have been delayed more than four hours … longer than it might take to drive. (If you are considering travel between a smaller airport and the SF Bay Area, September might be a good month to fly into Oakland or San Jose.)
  3. Flights that run very frequently. Some “premium” flights — for example, transcontinental flights — can be on the list. At time of writing, several of United’s “premium service” flights from Newark to San Francisco are often delayed from one to several hours. On the other hand, the airline has many options. If the airline has a high-status or high-revenue passenger making a connection, it’s not that hard for them to switch that passenger onto another flight.

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On the other hand, flights from Washington-Dulles (IAD) to SFO, which are less frequent, seem to be delayed less. And if, for example, United has a client going from IAD to Australia, or to Asia, via SFO, they have far fewer options to change them.

When a runway is closed or air traffic control is dealing with storms, realize that other factors will determine when your fight departs or lands.

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