FAQ - FREQUENTLY ASKED QUESTIONS
SERVICE HISTORY REPORT
2) DO YOU HAVE BY ROUTE BEFORE 1998?
3) DO YOU HAVE DATA BEFORE 1971?
4) WHY ARE AIRLINE NAMES USED BEFORE 1998, BUT NOT AFTER?
5) WHY ARE THERE SERVICE GAPS? THERE SHOULD BE MORE GAPS?
7) THERE IS NO INTERNATIONAL BEFORE 1998?
9) IS THERE A MINIMUM DEPARTURES?
10) HOW ARE REGIONAL AFFILIATES SHOWN?
2) DO YOU HAVE BY ROUTE BEFORE 1998?
No. If I did I would show it. It just isn't available in the data I have access to. The only place that is available are the Harvard Online archives which is only available to students and alumni for research and I do not have access to that.
3) DO YOU HAVE DATA BEFORE 1971?
Yes, but only for a small number of large carriers and at this time I only have data a few years before 1971 for those so it was not worth creating a third chart with limited coverage.
4) WHY ARE AIRLINE NAMES USED BEFORE 1998, BUT NOT AFTER?
Most of our users know airline codes, but fewer know the ones from that era, plus many were reused and it would be very confusing. I don't use names after 1998 because it doesn't require maintaining a current database. The old database doesn't change.
5) WHY ARE THERE SERVICE GAPS? THERE SHOULD BE MORE GAPS?
In the older data it is mostly operational data which means if there was a strike or other stoppage it will appear as a gap. There is also a cleaning process that removes one month aberrations. If a route stopped for a month or only operated for a month it is smoothed out.
6) IT'S WRONG?
It is what it is. There are surely errors in the data files as they were probably originally paper and converted. Also, some data is quarterly so I have had to assume service operated full quarters. There may also be any number of other issues.
7) THERE IS NO INTERNATIONAL BEFORE 1998?
That's a limitation of the data available to me.
8) THE AIRLINE NAME IS WRONG?
I did the best I could. There are also cases where the identifier used by the CAB/DOT was used for other airlines and there is no way to tell which carrier it was without manual editing which is too much.
9) IS THERE A MINIMUM DEPARTURES?
Generally from 1998 onward there is a 5 departure per month minimum, but prior to that there are a variety of filters as a number of different sources are used and some did not have departures.
10) HOW ARE REGIONAL AFFILIATES SHOWN?
Prior to 1998 they are primarily shown independently from their "parent" carrier, and from 1999 they are intended to be shown as part of their parent carrier's code.
11) WHAT AIRPORTS ARE AVAILABLE?
All existing airports are available, BUT large airports have so much data the charts exceed the maximum image size for Patreon.
12) WHAT DOES BLUE INDICATE?
Route data more than one month into the future is shown in blue to indicate it is still changing.
13) IS "MISSING" AN AIRLINE?
Missing means there was no carrier name attached to the service data. Often they were just marked as "XX" or "**". It could explain a gap in another carrier's data.
14) WHAT CHANGED IN JANUARY 2023?
The data prior to 1990 was upgraded using two new sources. One new source was a Southwest service history file that should fix issues with their exclusion from data sources because they were an intrastate carrier (this does not fix data for other intrastate carriers like PSA). Data from the National Archives used for the PERFORMANCE HISTORY REPORT was also integrated. Additionally, the airline database was upgraded with time periods for airline names that changed.
15) WHAT CHANGED IN MARCH 2023?
The data prior to 1990 was upgraded using a new source. Pacific Southwest Airlines (PSA/PS) and Air California (XK/OC) were intrastate carriers that did not report to DOT. Using timetables and other data the station history for their period as intrastate carriers has been updated. Note that there was a 70+ day stike shortly after deregulation began that may result in a brief service gap.PERFORMANCE HISTORY REPORT was also integrated. Additionally, the airline database was upgraded with time periods for airline names that changed.