We’ve been here before. (part 1 & part 2)  The US DoT datasets continue to be compromised by either deliberate misfilings or careless work efforts by some US airlines.  Users of these datasets are familiar with the shenanigans in Form 41.  But it seems the deliberate/careless nonsense is getting worse.  It’s time to name and shame.  The examples shared are in no specific order.

Delta Air Lines

This airline’s Form 41 filing is implausible.  Two examples demonstrate this.  The first is a chart of Delta’s direct maintenance costs per hour by aircraft type. 

Look at this nonsense.  A straight line?  It’s not even imaginative.

Since you might be thinking, what do the other airline filings look like?  Most certainly not a straight line, but rather a range over the Y-axis. It may not be entirely “honest,” but at least it’s plausible.  The Delta data is implausible. 

Next, look at Delta’s Form 41 filing on engine repair costs per air hour by aircraft type. How about these numbers?  Look a bit suspicious to you? Implausibly consistent – with various aircraft types and vintages priced the same. Notice that this “error” has been happening for years.

Southwest Airlines

One of the DoT’s most useful data sources is called the T2.  It is assembled from data filed under the T-100.  The T2 provides a great view on fuel burn.  We created a metric for calculating fuel burn per seat mile.  This metric allows for an equal comparison among aircraft at an airline, for example.  Or even an aircraft type among airlines.   An obvious item to look at is the change in fuel burn between the CEO/NEO and NG/MAX.  

Here is an example of what you would expect to see.   The numbers are approximately what Boeing and CFM guided the market to expect. The MAX9 delivers good fuel burn savings.  It is also the best single-aisle aircraft for carbon emissions because its fuel burn is low. Alaska’s numbers are a tad high but plausible. United’s numbers look plausible and consistent, averaging 16.8% and right where we expect the number to be.
For the MAX8, American Airlines’ numbers are eye-popping.  The MAX8 was grounded, and perhaps the data is still settling down, but we are uncomfortable with American’s numbers. 

And Southwest?  There is no way the MAX8 has a worse fuel burn than the 800NG. No Way.  We think Southwest misfiled 800NG data as MAX8.  Southwest flies most of the US MAX8 fleet, 156/234, which compromises the entire T2 MAX8 dataset.

We looked at fuel burn per air hour for the airline’s fleet for an additional check on the Southwest numbers.  The next table lists the results.  We are confident there is a significant data error in their filings. The 737-800 (738) fuel burn cannot have declined so much in 2021 and 2022.  And, of course, the 737 MAX8 (7M8) fuel burn cannot have risen by the numbers shown.  Moreover, our T2 audit shows Southwest’s MAX8 fleet flying an average of three hours/day in 2021 and 2022 – compared to 9.7 and 11.1 hours/day for the 737-800.

Spirit Airlines

Here’s another set of implausible T2 data.  The data for Frontier in 2018 makes no sense.  Since 2019, their numbers have been consistent but far higher than even Airbus could have dreamed.  The Spirit data is implausible and most likely mislabeling NEO and CEO. 

Breeze Airways

The last example is also from the T2 for 2022 and is a misfiling by Breeze. Breeze does not fly A320s.  This is most likely a miscode of A220.  Given Breeze’s size, such an error throws off their data.  When we notified DoT about this, we were advised, “…the carrier confirmed they are flying these aircraft types. Not much more I can do since the carrier confirmed.”  Um, the airline confirmed they fly A320s?  But they don’t.

So what?

US airlines file their data with the DoT per legal statute.  The main legal requirement falls under Section 329 (b):

(b) The Secretary shall-
(1) collect and disseminate information on civil aeronautics (other than that collected and disseminated by the National Transportation Safety Board under chapter 11 of this title), including, at a minimum, information on (A) the origin and destination of passengers in interstate air transportation (as that term is used in part A of subtitle VII of this title), and (B) the number of passengers traveling by air between any two points in interstate air transportation; except that in no case shall the Secretary require an air carrier to provide information on the number of passengers or the amount of cargo on a specific flight if the flight and the flight number under which such flight operates are used solely for interstate air transportation and are not used for providing essential air transportation under subchapter II of chapter 417 of this title;
2) study the possibilities of developing air commerce and the aeronautical industry; and
3) exchange information on civil aeronautics with governments of foreign countries through appropriate departments, agencies, and instrumentalities of the Government.

We contacted DoT about data errors in the past and found the OAI to be most helpful.  We have contacted Delta several times about its Form 41 data, and each request has been ignored.  Interestingly, if a carrier files inaccurate/poor/late data, it could be fined nearly $30,000, per day, per report. Do the math – it adds up fast if/when you get caught.

Another issue: Are there SEC implications for filing inaccurate data at DoT? We got three views from industry experts at the nexus of industry data: 

  • No connection; It’s a good check operationally. Not for balance sheet and cash flow.
  • Airlines use Form 41 as a starting point for their SEC filings. The data is slightly different from Form 41 to SEC filing requirements, but it’s helpful in forecasting, although it’s available with a huge lag.
  • Willfully filing inaccurate data would be a big problem for them.

It seems this issue has some sensitivity, but it may not have been tested.

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Co-Founder AirInsight. My previous life includes stints at Shell South Africa, CIC Research, and PA Consulting. Got bitten by the aviation bug and ended up an Avgeek. Then the data bug got me, making me a curious Avgeek seeking data-driven logic. Also, I appreciate conversations with smart people from whom I learn so much. Summary: I am very fortunate to work with and converse with great people.

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