Friday June 17 travel
It kinda turns into a high temperatures explainer
Welcome to our new readers—we're grateful that you're here! We're building deep learning algorithms to democratize flight delay predictions; until we launch, we're eager to synthesize things manually in our outlooks. These feature several recurring themes that we recognize may be unfamiliar or intimidating, so we’ve written explainers that tackle airport arrival rates, queuing delays in the airspace and different tools to distribute those delays. If there’s a topic or mechanism you’d like to see unpacked, please let us know (same goes for special travel occasions).
Over the last 5 days, the 7-day moving average of TSA throughput has climbed to levels not seen since February 2020. On one hand, the trend turning upwards again after a pre-Memorial Day Weekend stall is reassuring. And yet an apparent ceiling for single-day checkpoint volumes makes it difficult to muster much excitement.
The 7-day moving average is up 2.9% since May 19, but gains are largely attributable to a rising floor. Tuesday and Saturday, which were the two most lightly-traveled days in March and April, are up 4.0% and 5.4% week-over-four-week, respectively. Meanwhile, Friday and Sunday have found resistance over the same period: Friday is up just half of a percentage point and Sunday is down 0.6%. Perhaps surging fares have begun to push demand to shoulder weekdays. Regardless, it’s notable that day-of-week dispersions are tightening—nudging 2022 closer to 2019 patterns.
Whereas we felt our Holt-Winters model may have been too bearish in the past, tomorrow’s 54% probability to set a pandemic screening record1 feels a bit optimistic. We’re not uniformly pessimistic about tomorrow however. The weather setup is actually favorable, relatively speaking. In a first for these outlooks, heat will feature prominently in the narrative—a good thing insofar as it means [more disruptive] wind, rain and thunderstorms don’t play much of a role.
High temperatures
The dome of high pressure that is responsible for tomorrow’s warmth boasts quite the history, having produced record high temperatures in the Las Vegas-Houston corridor last Friday. By early this week, the heat had matriculated to the Central Plains, then Midwest and more recently the Southeast. The Southeast will remain the focus of this furnace tomorrow (with some lingering heat for Phoenix). More specifically, we’ll be focused on Atlanta (ATL) as well as Phoenix (PHX) and, to a lesser extent, Dallas-Fort Worth (DFW) and Charlotte (CLT).
High temperatures shouldn’t2 depress airport capacity, so we don’t expect to see the type of systemic constrains (e.g. ground delay program or ground stop) that we typically concern ourselves with. Nor do we expect temperatures will rise to the level that some aircraft plainly cannot operate (à la 2017). But aircraft performance isn’t binary—while we look to stay on the right side of operating limits, we think payload (read: passengers) will be restricted in some cases.
It’s really the intersection of hot temperatures and high altitudes3 that’s problematic, which is why we’re paying PHX and ATL more attention than DFW or CLT (ATL sneakily sits at 1,026’ elevation, barely 100’ feet below PHX). Additionally, payload restrictions are more likely on longer flights—these require more gas and until it’s combusted, fuel is just another form of weight that needs to be carried. Finally, smaller aircraft (i.e. regional jets that seat 44-79 passengers) are generally less capable.
Taken together, something like American’s 3:00 p.m. PHX-MSN (Madison, WI), when temperatures will be at their warmest, seems aspirational if fully booked. As does Delta’s 3:30 p.m. ATL-SBN (South Bend, IN). We’d further segment regional jets: For those that seat more than 50 passengers (like the one that operates PHX-MSN), trips longer than 1,250 miles are in the top 2.5% percent4 in terms of miles flown. For those aircraft that seat 50 or fewer passengers, 500 miles is an approximate threshold for the upper decile. Some airline apps include the distance flown; failing that, we’d point you to the always trusty Great Circle Mapper. Of course, if a payload-restricted flight is already booked underneath its adjusted capacity, any disruption should be largely imperceptible to passengers (perhaps a slight delay related to closer scrutiny of paperwork). Unfortunately in cases where a flight is booked above its adjusted capacity, airlines can be expected to deny passengers boarding (and compensation may not be required when weight and balance is the reason).
Heat will also drag on the productivity of baggage handlers (as well as other workgroups who spend most of their day outside), with airlines being careful to offer more breaks than normal. Though less acute than payload restrictions, this sluggishness is more difficult to pinpoint—it doesn’t discriminate by trip length or aircraft type. We’ll take the opportunity to remind readers to be kind to already-stretched airline agents.
Elsewhere
We’re also keeping an eye on Boston (BOS), Newark (EWR) and Seattle (SEA). For BOS, low ceilings for much of the day look to pressure airport capacity; the bigger question, however, will be whether convection develops during late afternoon ahead of an approaching cold front. The same cold front will swing through EWR, though weather models neglect to extend a line of broken storms south to the NYC area. But this is EWR we’re talking about, so even some good luck should be regarded with skepticism. To wit: winds will shift to the northwest behind the cold front, potentially setting up a suboptimal runway configuration.
Low pressure meanders inland over the Pacific Northwest, dropping ceilings to around 3,000’ for SEA. That’s low enough to introduce a 1 in 5 chance for arrival rates less than or equal to 40; scheduled5 arrival demand peaks at 47 (in the 8 p.m. hour).
In all “elsewhere” cases, we could use the benefit of one more TAF cycle to inform our predictions: We’ll craft a tweet-sized addendum later today that updates BOS, EWR and SEA.
Recommendations
Somewhat surprisingly, American has published a waiver for PHX related to high temperatures. Though the terms of the waiver don’t limit its use, we think applicability is relatively narrow. With that said, if you have a mid- or late afternoon layover in PHX and the outbound is a longer-stage regional flight, it might be worth looking for an alternate connecting point. There’s a lot of conditionals in there—a couple of which are on the technical side—so we’re happy to sort through any specific itineraries sent our way!
The current record is 2.45 million and belongs to the Sunday after Thanksgiving 2021.
File it under unreasonably pessimistic, but we could conceive of a scenario where the FAA anticipates aircraft will be unable to accept a relatively shorter runway for departure (say, PHX’s 7R-25L) and therefore proactively shifts some arrival capacity on longer runways to departures.
Both of which influence air density and, in turn, lift generation. For a better explanation of the underpinning physics, we’d suggest you check out this article from The Points Guy.
Of departures from ATL, CLT, DFW and PHX.
In terms of mainline concerns, the PHX-Hawaii schedule fortunately departs earlier in the day. Similarly, most of the international wide-body schedule departs late enough so as to avoid peak heat; AA’s 5:45 p.m. PHX-LHR is on the earlier side.
Cargo airlines as well as private jets are not included in scheduled demand and only become apparent when they file a flight plan (generally day-of). This unforeseen demand introduces the risk that delay probabilities/intensities are under-forecast.
Not for nothing, MSN’s main runway is out of service until 6/24. It’s not 106 here, but the longest available is just over 7000ft. For a few days 2 of 3 were closed and only the crosswind was open. That was… interesting. Probably a good thing AA and DL both retired their MD80’s…