**CDM Memorandum**

**Subject:** Minutes of the Daily Download Telcon of 19 January 1999

**To: ** Members of the Daily Download Task Force

**From: **Ken Howard and** **Rick Oiesen

**Date:** 30 January 1999

Participants in the first telcon on the daily download were Tammy Bowe
(NWA), Kris Frost (AWE), Ken Howard (Volpe), Patrick Metcalf (FSX),
Chris Pear (UAL), Rick Oiesen (Volpe), Steve Pierson (TWA), Tim Schmitz
(AAL), Joanne Stone (TWA), and Forrest Terral (ATCSCC).

# Goals of the Daily Download

Rick listed the overall goals of the daily download.

· To bring the schedule data in the CDM database in line with the
schedule data in the air carrier databases.

· To always have the OAG schedule data as a back-up in case there is a
problem with the daily download.

· To keep the process simple and reliable.

# ATCSCC Views

Since Forrest could not stay on for the entire telcon, we started by
discussing the Command Center concerns. Forest said that a fifteen hour
look-ahead time was sufficient, even for the long run. He also liked the
idea of an air carrier requesting its schedule from the CDM string so it
would know what the CDM string thought its schedule was; it could then
make corrections as necessary.

# Air Carrier Experience with the Daily Download

We next heard from each air carrier that already sends in data for all
its flights to see what that told us about the daily download.

*TWA. *Joanne described TWA's experience. At 0900Z each morning TWA
sends in data on all the flights in the day's schedule. A flight plan is
calculated for each flight using the forecast winds; the times from
these calculations are sent in the messages to the CDM string. It takes
about thirty minutes to do all these calculations and to send the data,
where most of this time is spent calculating the flight plans. Joanne
finds that the ETEs in these flight plans are much more accurate than
the ETEs in the OAG.

Joanne said that after all the messages are sent in, TWA compares the
flights that are flying to those in the OAG and sends in an FX for those
that are not flying. The problem is that she doesn't know if the copy of
the OAG that she uses is the same as the copy that Volpe is using.

*AAL. *Tim Schmitz described AAL's experience. Eleven hours before a
flight is scheduled to depart, a message is sent in, even if the data is
the same as is in the OAG. A flight plan is not calculated at this time.
A flight plan is calculated four hours prior to departure; this usually
causes a message to be sent to the CDM string since a message is sent if
any time changes by even a minute. AAL does not look at the OAG and send
cancels as TWA does.

Tim speculated on what it would be like if AAL changed to sending in a
daily download all at once. He thought that since AAL sends its messages
over AOCnet, it could send messages on the 4000 AAL and EGF flights in
probably less than a minute.

Tim said that the number of hours prior to departure that the message
was sent for a flight was a parameter that could be changed, e.g., to
twenty-four hours. Rick suggested that he change it to fifteen hours
since this was the look-ahead period in ADLs; this would also test that
this parameter could be changed without fouling anything up.

*AWE.* Kris Frost described AWE's experience. AWE sends in messages on
all flights for the day at 0500Z. Flight plans are not calculated, so
the scheduled times are sent. FXs are not sent based on the OAG. Kris
reported that she has been having some internal problems with her
network, so she is considering changing to an incremental download.

# What Should Be Done?

We next entered the free-for-all part of the telcon in which we
discussed what should be done.

Tammy was leaning toward alternative 1 of Rick's memo of December 23 in
which an air carrier sends in the day's flights all at once and then
Volpe removes flights that have only OAG data. But she asked what
happened if an air carrier failed in the middle of its daily download.
Rick replied that this would not hurt anything as long as Volpe did not
receive a message that the daily download was completed; it would only
be upon receiving this message that any flights were removed.

There was still the possibility that the air carrier might send the
message saying that the daily download was completed even though perhaps
a bunch of messages in the middle had been lost. Ken proposed that if
Volpe deleted any flights, it would send a message back to the air
carrier that listed the flights that were deleted; the air carrier could
then check this list to be sure that no good flights had been deleted.
Everyone immediately agreed that a message to the air carrier that
showed the deleted flights was a necessity. In addition, Ken said, there
could be rules that Volpe could follow, e.g., not delete flights if more
than a hundred needed to be deleted; this would guard against this sort
of problem.

Ken also made a point that became a theme of his remarks throughout the
telcon. He said that we might want to skip the step of Volpe removing
flights from the OAG based on the daily download since we might delete
some good flights. Ken urged everyone to think of the daily download as
a way to correct the OAG, not a way to cancel flights. If Volpe removed
flights based on the daily download, Ken saw there being a real danger
of some good flights being removed.

Ken kept reminding everyone to keep in perspective the benefit of the
daily download. He said that the data archive that Volpe has been
collecting shows that the problem of there being bad flights in the OAG
is not as severe as we had previously thought; this is shown by there
being a relatively small number of time-out cancels of flights for which
the CDM string had only OAG data. Therefore, he sees a real danger that
if we remove bad flights, we might remove good flights as well because
of some misunderstanding or lost messages, and the daily download could
end up hurting the CDM database rather than helping. Ken took the action
item of making available some statistics on time-out cancels of flights
with OAG data only so everyone could see what he was talking about.

Tammy suggested that we find out why there are bad flights in the OAG
and fix the problem at the root. Ken responded by giving a historical
perspective and saying that cleaning up the OAG has been a continuing
problem. We find one problem, fix it, and then another problem crops up,
and this has continued for years. Therefore, while we should continue to
clean up the OAG, it isn't possible to fix it once so that it will stay
fixed.

Tim talked about the possibility of the air carriers sending in the data
two or three days in advance so there would be plenty of time to correct
it. Ken responded by saying that he would prefer to get rid of the
Future Flights database, which Volpe now maintains. We allow air
carriers to send in messages as much as eleven months in advance. Ken
sees the Future Flights database as being bug-prone. For example, he
will sometimes see a message from this database that is six months old
being processed; he wonders if this is good data and if the air carrier
even knows about this message. He prefers the idea of deciding what
look-ahead period is needed for traffic management and then having the
air carriers send in data at that time.

We moved on to the second alternative of Rick's memo, in which at the
end of the daily download the CDM string would send the air carrier what
the CDM string thought its schedule was. The air carrier could then
inspect this and make sure that the CDM string had the correct data. The
term "re-sync message" was used to refer to this message from the CDM
string that shows an air carrier's schedule

Forrest said that he really liked this idea of the air carrier being
able to make sure that the data in the CDM string was exactly correct.
Joanne thought that the re-sync message was a great idea. Tammy said
that she liked the idea, but the problem was that she didn't know when
NWA could come up with the resources to do this. We speculated that
other air carriers would also face this resource problem. Kris said that
she wants the re-sync message but maybe not for a year.

Ken outlined Mark Klopfenstein's idea that an air carrier not do a full
download but only send in a list of the flights that are operating.
Volpe would then delete the flights not on the list.

# Miscellany

Joanne stressed that an air carrier should not lose slots that it should
have because of the daily download, and all agreed. There was some
discussion of the distinction between 'good' slots that the air carrier
should keep because they represented a real flight that happened not to
be flying and 'bad' slots that an air carrier should not keep because
they represented not a real flight but rather inaccurate data in the
OAG. We agreed for the present to table the discussion of slots. We will
first deal with the technical issue of how to exchange all this data in
a reliable way.

There was also some discussion of whether the time in the OAG or the
time in the daily download should be used for ration-by-schedule. This
topic was also tabled for the present.

Several times during the discussion Ken stressed the need for an air
carrier to have a way to recover if its data feed is down for a while.
For example, if the feed of CDM schedule messages to Volpe is down for
three hours, the air carrier needs to be able to resend the messages
that were lost during that three hour period. Tim said that AAL already
has this capability, and it is easy to activate, but it does take human
action. Tim suggested that this could be automated. Ken thought that all
the airlines needed this capability.

Tim brought up the problem of code-sharing. Suppose that two air
carriers, one a CDM participant and one a non-participant, both have
flight numbers for a flight. Suppose that the flight is cancelled, and
the CDM participant sends in an FX for its flight. What about the other?
Nobody had anything brilliant to say on this.

# Summary

Joanne summarized with a possible scheme.

1\. An air carrier sends in messages for some interval ahead.

2\. The air carrier tells Volpe that the daily download is complete for
that interval.

3\. Volpe removes from the CDM database any flights for which there is
only OAG data and tells the air carrier what flights these are.

4\. The air carrier examines this list of deleted flights and takes
action as necessary.

5\. The re-sync message is a future enhancement.

We decided that alternatives 2 and 3 of Rick's memo are knocked out of
consideration since they depend on the air carriers processing the
re-sync message as a critical part of the daily download; this doesn't
seem to be in the cards in the immediate future because of air carrier
resource limitations.

By the time the telcon had gone on for an hour and a half, we were all
slap happy and didn't know what progress we had made if any. We decided
to adjourn, think things over, and re-convene at a later date.