- more flights are cancelled today when there is a question of aircraft reliability
- fewer flights are cancelled today when there would be a long delay*
That hypothesis could get you more very long delays, fewer safety accidents, and roughly constant cancellation rates. Maybe it also helps explain why we do not observe increases in minor delays after 1997 (if minor delays didn’t usually result in cancellation in the past), which I think we would expect from the congestion hypothesis.
*why would that be? Maybe to offset increased safety related cancellations? Maybe because airports are nicer and customers are more willing to wait in them? Not sure if that’s true. Or maybe it’s cheaper than booking everyone hotels? Or maybe it’s a consequence of greater logistical sophistication enabling airlines to avoid cascading problems from allowing flights to run very late?
Hmm that's interesting. Maybe one reason airlines are keeping more delayed flights instead of cancelling them is because each flight has a lot more people on average, so the compensation and rebooking would be more difficult.
I do also agree that we should expect a rise in both shirt and long delays from the congestion hypothesis, but congestion + schedule padding can explain rising long delays and falling/stable short delays.
Very helpful data-grounded discussion piece. 😍 To add an airliner perspective on why flight times are scheduled to be longer: Airports have become significantly larger and more sprawling. Taxiing (the time between gate and runway, either on arrival or departure) probably takes a few minutes longer. Of course this is partially due to "congestion" (a "bad" thing), but there is also an element of infrastructure just getting more developed (a "good" thing). Also, flights spend more time in holding patterns, and airlines plan for that. E.g., scheduled flight times from A to B may be 10min longer than the return flight from B to A. Holding patterns probably fall completely under the "congestion" header, as this is a function mainly of having sufficiently runways and airspace around the airport.
As a former airline pilot I challenge your claims. I suspect that, if anything, there is far less holding now than there used to be. This is because the airlines tend to carry minimum fuel (to save on weight, and thus fuel) and when things go wrong, they divert a lot more quickly than they used to. This is net worse for everyone than holding, but is less holding, not more.
I'm not sure about larger and more sprawling airports--this is true in some places (the new runway at ATL for instance), but the original article indicates that there's been almost no new runway construction.
I am not familiar with domestic US airline ops, only international airlines operating into US. But can confirm that generally, how much fuel gets taken is more monitored (bc you burn around 3% of extra fuel per hour, which impacts costs). Probably aircraft carry less fuel than in 1990, adjusted by stage length. But I am not sure whether there is a data source to confirm this - and whether the impact of diversions is material to affect delays. Let's keep in mind that diversions are awfully expensive from a financial perspective (extra fuel for extra leg, extra airport fees, affecting crew rosters), so I am sure no airline is happy to have so many diversions that these extra costs overcompensate the fuel savings.
As for airport size - agree, not too many runways were added across the US, but terminals were either remodeled, extended or built from scratch. Just take JFK - T1 in 1998, T4 2001, T5 in 2008, T8 in 2007. Not all of these were totally new, but you added new taxiways, aprons were remodeled, etc. This adds to taxiing times. 5min more is already material.
I have noticed this same phenomenon and it's an excellent thing. The problem with a delayed flight is not the wait to depart, it's the missing of scheduled events, such as connecting flights, by arriving late. By padding their schedules they provide travellers with much lower-risk timetables, and arriving early is practically never an inconvenience. This is not perfidy, this is sensible timetabling.
It's just that the base rate of 2 is still quite low; one or two percent of flights.
So the severe delays can go up by 4x, but if short delays go down by 30% because of the schedule padding, that can totally mask the number of 15+ minute delays because the vast majority are the short delays that are going down in frequency.
15+ minute delays have remained stable, but 1+, 1.5+, and 3hr+ delays have all grown, which means that 15-45 minute delays must have declined, since 15+ is the sum of all the delay lengths.
Just came from 3 weeks in Bali. Both airports in Indonesia were beautiful, efficient and a pleasure to arrive and depart from. Unfortunately we left from LAX and returned to LAX. LAX was perhaps the low point of the trip in both directions. Dim and dingy. Long lines that did not exist in the other places. No signage directing passengers which way to go. I was so disappointed. The amount of tax money that is spent on continuous remodeling is going into a hole somewhere. Another example of bad California politics.
Not sure it's a CA thing. JFK is very similar to your description of LAX, whereas SFO is world-class, beautiful and efficient and comfortable despite being run by the city government of SF.
I’d bet there’s a trade off between very long delays and cancellations. (I also think there’s been some regulatory changes affecting how airlines think about delay vs cancellation.) What’s the trend look like for the combined rate of cancellations/very long delays?
Well delays are growing a lot and cancellations are basically staying stable on average or even getting slightly more common, so the combined trend is still going to be increasing
> The connection between this financialization of air travel to increasing delays is difficult to make explicit, but something about the coincidence of credit-card-mile loans shifting transportation into a loss-leader sector, airfare prices falling, and a rapid increase in the rate of long delays is too suggestive to ignore.
The obvious question is, if the airlines make so much money on credit cards but lose so much on air transport, why not just stop doing the air transport? And of course, the answer is "nobody will use your credit card if your air transport offering sucks". In-cabin quality (outside basic economy) has improved substantially in the past two decades, especially on Delta and United; they need to keep investing in this to keep the miles / credit card dollars flowing, so I'm not sure it's fully accurate to treat these as two independent lines of business.
Nice piece! An alternative hypothesis:
- more flights are cancelled today when there is a question of aircraft reliability
- fewer flights are cancelled today when there would be a long delay*
That hypothesis could get you more very long delays, fewer safety accidents, and roughly constant cancellation rates. Maybe it also helps explain why we do not observe increases in minor delays after 1997 (if minor delays didn’t usually result in cancellation in the past), which I think we would expect from the congestion hypothesis.
*why would that be? Maybe to offset increased safety related cancellations? Maybe because airports are nicer and customers are more willing to wait in them? Not sure if that’s true. Or maybe it’s cheaper than booking everyone hotels? Or maybe it’s a consequence of greater logistical sophistication enabling airlines to avoid cascading problems from allowing flights to run very late?
Hmm that's interesting. Maybe one reason airlines are keeping more delayed flights instead of cancelling them is because each flight has a lot more people on average, so the compensation and rebooking would be more difficult.
I do also agree that we should expect a rise in both shirt and long delays from the congestion hypothesis, but congestion + schedule padding can explain rising long delays and falling/stable short delays.
Very helpful data-grounded discussion piece. 😍 To add an airliner perspective on why flight times are scheduled to be longer: Airports have become significantly larger and more sprawling. Taxiing (the time between gate and runway, either on arrival or departure) probably takes a few minutes longer. Of course this is partially due to "congestion" (a "bad" thing), but there is also an element of infrastructure just getting more developed (a "good" thing). Also, flights spend more time in holding patterns, and airlines plan for that. E.g., scheduled flight times from A to B may be 10min longer than the return flight from B to A. Holding patterns probably fall completely under the "congestion" header, as this is a function mainly of having sufficiently runways and airspace around the airport.
As a former airline pilot I challenge your claims. I suspect that, if anything, there is far less holding now than there used to be. This is because the airlines tend to carry minimum fuel (to save on weight, and thus fuel) and when things go wrong, they divert a lot more quickly than they used to. This is net worse for everyone than holding, but is less holding, not more.
I'm not sure about larger and more sprawling airports--this is true in some places (the new runway at ATL for instance), but the original article indicates that there's been almost no new runway construction.
I am not familiar with domestic US airline ops, only international airlines operating into US. But can confirm that generally, how much fuel gets taken is more monitored (bc you burn around 3% of extra fuel per hour, which impacts costs). Probably aircraft carry less fuel than in 1990, adjusted by stage length. But I am not sure whether there is a data source to confirm this - and whether the impact of diversions is material to affect delays. Let's keep in mind that diversions are awfully expensive from a financial perspective (extra fuel for extra leg, extra airport fees, affecting crew rosters), so I am sure no airline is happy to have so many diversions that these extra costs overcompensate the fuel savings.
As for airport size - agree, not too many runways were added across the US, but terminals were either remodeled, extended or built from scratch. Just take JFK - T1 in 1998, T4 2001, T5 in 2008, T8 in 2007. Not all of these were totally new, but you added new taxiways, aprons were remodeled, etc. This adds to taxiing times. 5min more is already material.
I have noticed this same phenomenon and it's an excellent thing. The problem with a delayed flight is not the wait to depart, it's the missing of scheduled events, such as connecting flights, by arriving late. By padding their schedules they provide travellers with much lower-risk timetables, and arriving early is practically never an inconvenience. This is not perfidy, this is sensible timetabling.
I can't wrap my head around two things you show:
1. Flights are taking longer now than in 1990, but airlines are scheduling them to be substantially longer.
2. There is a sharp rise in severe delays, as measured by actual vs scheduled without corrections
1 acts to decrease the reported delay figures, 2 acts to increase it - so my sleepy brain is struggling to fit both together
It's just that the base rate of 2 is still quite low; one or two percent of flights.
So the severe delays can go up by 4x, but if short delays go down by 30% because of the schedule padding, that can totally mask the number of 15+ minute delays because the vast majority are the short delays that are going down in frequency.
But you show that short delays have remained stable?
15+ minute delays have remained stable, but 1+, 1.5+, and 3hr+ delays have all grown, which means that 15-45 minute delays must have declined, since 15+ is the sum of all the delay lengths.
Got it, I thought they were intervals like 15 mins - 1 hr, 1hr - 1.5hr, etc
Just came from 3 weeks in Bali. Both airports in Indonesia were beautiful, efficient and a pleasure to arrive and depart from. Unfortunately we left from LAX and returned to LAX. LAX was perhaps the low point of the trip in both directions. Dim and dingy. Long lines that did not exist in the other places. No signage directing passengers which way to go. I was so disappointed. The amount of tax money that is spent on continuous remodeling is going into a hole somewhere. Another example of bad California politics.
Not sure it's a CA thing. JFK is very similar to your description of LAX, whereas SFO is world-class, beautiful and efficient and comfortable despite being run by the city government of SF.
I’d bet there’s a trade off between very long delays and cancellations. (I also think there’s been some regulatory changes affecting how airlines think about delay vs cancellation.) What’s the trend look like for the combined rate of cancellations/very long delays?
Well delays are growing a lot and cancellations are basically staying stable on average or even getting slightly more common, so the combined trend is still going to be increasing
> The connection between this financialization of air travel to increasing delays is difficult to make explicit, but something about the coincidence of credit-card-mile loans shifting transportation into a loss-leader sector, airfare prices falling, and a rapid increase in the rate of long delays is too suggestive to ignore.
The obvious question is, if the airlines make so much money on credit cards but lose so much on air transport, why not just stop doing the air transport? And of course, the answer is "nobody will use your credit card if your air transport offering sucks". In-cabin quality (outside basic economy) has improved substantially in the past two decades, especially on Delta and United; they need to keep investing in this to keep the miles / credit card dollars flowing, so I'm not sure it's fully accurate to treat these as two independent lines of business.
Yes, this is a known problem when people try to disentangle a business into clean line items (e.g. "Costco operating losses vs. membership fees").
Still, it's always surprising to people when the typical transaction (viewed individually) they associate with a company is not profitable