I am researching how much commercial airline disruption was caused by
the 11th September attacks.

Ideally what is required is a day to day breakdown (from and including
12th September 2001, to and including 25th September 2001) of the
number and percentage of flights in the air (for 3 major US airline
companies) on each day during that period, relative to the number of
flights which would normally be in the air on each of those days.

This would take the format of -

"According to Authority X, there were X number of flights in operation
by X airline company on [13th] September 2001, representing X % of
normal flight services. This number and percentage rose to X and X %
on 14th September 2001 ....[up to 25th September 2001)".

I can limit the information you provide me to 3 major airlines, if
possible. Ideally the information should cover American, United and
Delta, but if you cannot get information on these airlines,
information regarding Northwest, Continental, Southwest and/or
Frontier would be fine.

In the alternative, a number and percentage breakdown of flights per
day, per major airport would be useful (for example, O'Hare, Kennedy,
Atlanta). However a breakdown per airline is the priority.

I have information on a day-to-day basis for Alaska Airlines up to
20th September 2001, which provides an ideal format - the link is
http://www.alaskaair.com/ASCorpInfo/Latest.asp

I know that the FAA shut down commercial airspace at 945 ET on
Tuesday, 11th September 2001 and reopened it to US airlines at 1100 ET
on Thursday, 13th September 2001. It was reopened to private aircraft
owners at 1600 ET on 13th September 2001. There was limited flight
activity on Wednesday 12th September 2001 to allow diverted aircraft
to continue to their destinations, or be repositioned.

Please cite details of the exact sources referenced to acquire the
information you use in your report.

Many thanks.

Hello Garrettm, and thanks for a very interesting question.  Even the
cold, hard numbers of flight data have a chilling effect when the
timeframe in question is beofre and after 9/11/2001.

I felt sure that the information you were seeking existed somewhere in
the vast archives of data kept by the U.S. government.  The challenge
was finding it, and then pulling out just what you needed. 
Fortunately, the Federal Aviation Administration has a well organized
web page that led me to US Department of Transporation, Bureau of
Transportation Statistics, and specifically to the web page of Air
Travel Consumer Report Data at:

http://199.79.179.77/oai/atcr/

where you will find a report entitled:  "Number of Flights,
Cancellations, and Late Arrivals by Day and Carrier" for Septmeber
2001 (or any other month of interest)available as a PDF or HMTL or
spreadsheet or comma delimited file.  I downloaded the spreadsheet and
extracted the information you are seeking which I've reproduced below.

Note that the percentage figures are data that I calculated from the
DOT numbers, rather than something they provided in the original
table.  If the numbers do not format properly when you access this
answer (as sometimes happens in Google Answers -- it's hard to know
how the final answer will actuall apppear) then you can either (1) let
me know, and I'll upload the file to a site where you can retrieve it,
or (2) you can access the data yourself at the above-mentioned web
site, and get all the numbers you want (including for other, smaller
airlines), for September and beyond.

I hope this meets your needs.  If you need any additional information,
please let me know through the "Request for Clarification" before
rating this answer.
And good luck with your research.  

-----

Number of Flights and Cancellations by Day and Carrier, September 2001
 (Domestic Flights)
					
					
					
		Number of	Number of	Percent of Actual 	
Carrier	Date	 Actual Flights	Cancellations	Flights on 9/10/01	
					
 Total	9/10/2001	16905	661	 100.00%	
 All 	9/11/2001	2542	14962	 15.04%	
air-    9/12/2001	0	17535	 0.00%	
lines	9/13/2001	1445	16109	 8.55%	
	9/14/2001	7745	9611	 45.81%	
	9/15/2001	9634	5573	 56.99%	
	9/16/2001	12243	4297	 72.42%	
	9/17/2001	13708	3518	 81.09%	
	9/18/2001	13799	3402	 81.63%	
	9/19/2001	14321	2888	 84.71%	
	9/20/2001	14249	2946	 84.29%	
	9/21/2001	14229	2970	 84.17%	
	9/22/2001	12431	2457	 73.53%	
	9/23/2001	13852	1902	 81.94%	
	9/24/2001	14303	1515	 84.61%	
	9/25/2001	14325	1421	 84.74%	
	9/26/2001	14355	1312	 84.92%	
	9/27/2001	14393	987	 85.14%	
	9/28/2001	14436	643	 85.39%	
	9/29/2001	12596	1070	 74.51%	
	9/30/2001	13730	636	 81.22%	
					
					
American	
        9/10/2001	2043	71	100.00%	
 	9/11/2001	288	1802	14.10%	
 	9/12/2001	0	2106	0.00%	
 	9/13/2001	139	1973	6.80%	
 	9/14/2001	679	1195	33.24%	
 	9/15/2001	831	927	40.68%	
 	9/16/2001	1270	551	62.16%	
 	9/17/2001	1316	559	64.42%	
 	9/18/2001	1304	572	63.83%	
 	9/19/2001	1304	571	63.83%	
 	9/20/2001	1315	563	64.37%	
 	9/21/2001	1317	557	64.46%	
 	9/22/2001	1251	510	61.23%	
 	9/23/2001	1496	16	73.23%	
 	9/24/2001	1574	8	77.04%	
 	9/25/2001	1573	9	76.99%	
 	9/26/2001	1575	3	77.09%	
 	9/27/2001	1577	4	77.19%	
 	9/28/2001	1571	10	76.90%	
 	9/29/2001	1490	4	72.93%	
 	9/30/2001	1521	4	74.45%	
					
					
					
Continental	
        9/10/2001	1088	57	100.00%	
 	9/11/2001	195	929	17.92%	
 	9/12/2001	0	1128	0.00%	
 	9/13/2001	0	1147	0.00%	
 	9/14/2001	382	774	35.11%	
 	9/15/2001	385	366	35.39%	
 	9/16/2001	538	475	49.45%	
 	9/17/2001	948	196	87.13%	
 	9/18/2001	928	195	85.29%	
 	9/19/2001	920	209	84.56%	
 	9/20/2001	878	265	80.70%	
 	9/21/2001	901	257	82.81%	
 	9/22/2001	637	70	58.55%	
 	9/23/2001	812	74	74.63%	
 	9/24/2001	873	106	80.24%	
 	9/25/2001	870	98	79.96%	
 	9/26/2001	866	22	79.60%	
 	9/27/2001	875	5	80.42%	
 	9/28/2001	885	8	81.34%	
 	9/29/2001	629	9	57.81%	
 	9/30/2001	840	8	77.21%	
					
					
					
Delta	9/10/2001	2277	114	100.00%	
 	9/11/2001	420	1969	18.45%	
 	9/12/2001	0	2389	0.00%	
 	9/13/2001	465	1924	20.42%	
 	9/14/2001	1168	1222	51.30%	
 	9/15/2001	1675	690	73.56%	
 	9/16/2001	1977	398	86.82%	
 	9/17/2001	1947	400	85.51%	
 	9/18/2001	1997	348	87.70%	
 	9/19/2001	1958	387	85.99%	
 	9/20/2001	1976	349	86.78%	
 	9/21/2001	1971	321	86.56%	
 	9/22/2001	1926	308	84.58%	
 	9/23/2001	1946	290	85.46%	
 	9/24/2001	1980	250	86.96%	
 	9/25/2001	1964	235	86.25%	
 	9/26/2001	1979	220	86.91%	
 	9/27/2001	1974	126	86.69%	
 	9/28/2001	1979	38	86.91%	
 	9/29/2001	1962	29	86.17%	
 	9/30/2001	1953	49	85.77%	
					
					
					
American Eagle
        9/10/2001	1337	136	100.00%	
 	9/11/2001	228	1248	17.05%	
 	9/12/2001	0	1478	0.00%	
 	9/13/2001	156	1320	11.67%	
 	9/14/2001	655	822	48.99%	
 	9/15/2001	979	324	73.22%	
 	9/16/2001	1291	133	96.56%	
 	9/17/2001	1326	150	99.18%	
 	9/18/2001	1310	169	97.98%	
 	9/19/2001	1209	271	90.43%	
 	9/20/2001	1154	327	86.31%	
 	9/21/2001	1164	317	87.06%	
 	9/22/2001	1015	288	75.92%	
 	9/23/2001	1113	310	83.25%	
 	9/24/2001	1154	327	86.31%	
 	9/25/2001	1172	308	87.66%	
 	9/26/2001	1140	342	85.27%	
 	9/27/2001	1136	346	84.97%	
 	9/28/2001	1135	346	84.89%	
 	9/29/2001	996	308	74.50%	
 	9/30/2001	1072	353	80.18%	
					
					
					
Northwest
        9/10/2001	1531	47	100.00%	
 	9/11/2001	269	1309	17.57%	
 	9/12/2001	0	1578	0.00%	
 	9/13/2001	88	1490	5.75%	
 	9/14/2001	742	835	48.47%	
 	9/15/2001	970	366	63.36%	
 	9/16/2001	1199	263	78.31%	
 	9/17/2001	1273	305	83.15%	
 	9/18/2001	1273	305	83.15%	
 	9/19/2001	1279	299	83.54%	
 	9/20/2001	1259	319	82.23%	
 	9/21/2001	1275	302	83.28%	
 	9/22/2001	1152	48	75.24%	
 	9/23/2001	1223	54	79.88%	
 	9/24/2001	1272	54	83.08%	
 	9/25/2001	1264	62	82.56%	
 	9/26/2001	1266	60	82.69%	
 	9/27/2001	1275	45	83.28%	
 	9/28/2001	1274	45	83.21%	
 	9/29/2001	1139	37	74.40%	
 	9/30/2001	1225	23	80.01%	
					
					
					
TWA	9/10/2001	683	15	100.00%	
 	9/11/2001	107	591	15.67%	
 	9/12/2001	0	698	0.00%	
 	9/13/2001	140	556	20.50%	
 	9/14/2001	474	222	69.40%	
 	9/15/2001	559	37	81.84%	
 	9/16/2001	592	17	86.68%	
 	9/17/2001	629	21	92.09%	
 	9/18/2001	558	92	81.70%	
 	9/19/2001	619	33	90.63%	
 	9/20/2001	628	12	91.95%	
 	9/21/2001	640	0	93.70%	
 	9/22/2001	590	0	86.38%	
 	9/23/2001	601	0	87.99%	
 	9/24/2001	637	3	93.27%	
 	9/25/2001	637	2	93.27%	
 	9/26/2001	634	6	92.83%	
 	9/27/2001	640	0	93.70%	
 	9/28/2001	632	4	92.53%	
 	9/29/2001	586	4	85.80%	
 	9/30/2001	595	2	87.12%	
					
					
					
United	9/10/2001	2077	72	100.00%	
 	9/11/2001	254	1895	12.23%	
 	9/12/2001	0	2148	0.00%	
 	9/13/2001	0	2148	0.00%	
 	9/14/2001	366	1783	17.62%	
 	9/15/2001	405	1609	19.50%	
 	9/16/2001	527	1545	25.37%	
 	9/17/2001	911	1239	43.86%	
 	9/18/2001	1085	1065	52.24%	
 	9/19/2001	1677	473	80.74%	
 	9/20/2001	1712	437	82.43%	
 	9/21/2001	1726	425	83.10%	
 	9/22/2001	1633	380	78.62%	
 	9/23/2001	1700	368	81.85%	
 	9/24/2001	1713	42	82.47%	
 	9/25/2001	1705	48	82.09%	
 	9/26/2001	1712	44	82.43%	
 	9/27/2001	1722	35	82.91%	
 	9/28/2001	1712	39	82.43%	
 	9/29/2001	1630	15	78.48%	
 	9/30/2001	1611	6	77.56%	
					
					
					
US Airways
        9/10/2001	1875	111	100.00%	
 	9/11/2001	386	1599	20.59%	
 	9/12/2001	0	1986	0.00%	
 	9/13/2001	183	1803	9.76%	
 	9/14/2001	748	1235	39.89%	
 	9/15/2001	957	851	51.04%	
 	9/16/2001	1170	753	62.40%	
 	9/17/2001	1524	454	81.28%	
 	9/18/2001	1554	424	82.88%	
 	9/19/2001	1538	438	82.03%	
 	9/20/2001	1542	437	82.24%	
 	9/21/2001	1402	576	74.77%	
 	9/22/2001	1096	712	58.45%	
 	9/23/2001	1311	611	69.92%	
 	9/24/2001	1300	678	69.33%	
 	9/25/2001	1357	619	72.37%	
 	9/26/2001	1385	592	73.87%	
 	9/27/2001	1398	402	74.56%	
 	9/28/2001	1455	122	77.60%	
 	9/29/2001	1138	620	60.69%	
 	9/30/2001	1306	159	69.65%	
					
					
					
Southwest
        9/10/2001	2759	23	100.00%	
 	9/11/2001	337	2433	12.21%	
 	9/12/2001	0	2778	0.00%	
 	9/13/2001	0	2778	0.00%	
 	9/14/2001	1788	991	64.81%	
 	9/15/2001	1936	215	70.17%	
 	9/16/2001	2591	20	93.91%	
 	9/17/2001	2754	24	99.82%	
 	9/18/2001	2718	60	98.51%	
 	9/19/2001	2750	28	99.67%	
 	9/20/2001	2721	57	98.62%	
 	9/21/2001	2739	40	99.28%	
 	9/22/2001	2136	15	77.42%	
 	9/23/2001	2607	4	94.49%	
 	9/24/2001	2767	11	100.29%	
 	9/25/2001	2745	33	99.49%	
 	9/26/2001	2761	17	100.07%	
 	9/27/2001	2755	23	99.86%	
 	9/28/2001	2756	23	99.89%	
 	9/29/2001	2128	23	77.13%	
 	9/30/2001	2586	25	93.73%

---

Clarification of Answer by pafalafa-ga on 03 Feb 2003 11:10 PST

As I thought, the answer didn't format very neatly, so I've posted the
file on at the following web address, where it will be available
temporarily (not more than 30 days):

www.lucidmatrix.com/uploads/airlines post 9-11.txt 

Again, let me know if there is anything I can do to improve on this
answer.

---

Clarification of Answer by pafalafa-ga on 04 Feb 2003 03:19 PST

Whoops...the link needs to look like this in order to access
it...sorry for any confusion:

http://www.lucidmatrix.com/uploads/airlines%20post%209-11.txt

Excellent response in both content and time taken. Many thanks.

Hello Garrettm,

I could assemble results for the following airlines:

----

Northwest
http://www.nwa.com/corpinfo/upclose/2000.shtml

Sept. 11 - "Northwest also announces that all flights are cancelled
indefinitely. All domestic and international Northwest Airlines
flights are accounted for and safe."

Sept. 14 - "Northwest Airlines resumes limited commercial service."

Sept. 15 - "Northwest will reduce its system-wide flight schedule by
20 percent as measured on an available seat mile basis. The carrier
takes this action because of the Sept. 11 terrorist attacks (...) and
the resulting reduction in passenger demand and new airport and
airline security measures. (...)"

Sept. 21 - "Northwest announces a reduction in staffing levels by
approximately 10,000 employees. The carrier takes this action because
of the Sept. 11 terrorist attacks (...)"

----

Continental
http://www.continental.com/vendors/default.asp?SID=597D484120524BDDA4621EB026F60507&i=PRNews

Sept. 11 - "All Continental Airlines (NYSE: CAL) aircraft have been
accounted for and are safe. The U.S. government has asked all carriers
to land airplanes at the nearest airports"

Sept. 12 - No "commercial airline has been given approval to resume
operations. As a result, Continental Airlines (NYSE: CAL) expects to
operate only minimal flights today, consisting principally of the
continuation of flights that were diverted yesterday."

Sept. 13 - Continental Airlines "is prepared to operate up to 50
percent of its regularly scheduled flights on Friday, Sept. 14."

Sept. 14 - Continental Airlines "is prepared to operate up to 55
percent of its regularly scheduled flights on Saturday, Sept. 15.
(...) Continental and Continental Express expect to complete almost
half of their typical schedule of more than 2,000 daily flights today"

Sept. 15 - Continental Airlines announced "that it will immediately
reduce its long-term flight schedule by approximately 20 percent on a
systemwide available seat mile basis, and will be forced to furlough
approximately 12,000 employees in connection with this reduction."

Sept. 17 - Average of "18 percent reduction in flights" to Cleveland,
Houston, Newark. Several routes, like Cleveland and London/Gatwick,
are temporarily suspended. Complete discontinuation of 10 cities,
including Houston-Abilene, Houston-San Angelo.


Continental Airlines states the following in a press release from
Sept. 9/20/2001:
http://ir.thomsonfn.com/InvestorRelations/PubNewsStory.aspx?partner=Mzg0TkRnMU1RPT1QJFkEQUALSTO&product=MzgwU1ZJPVAkWQEQUALSTOEQUALSTO&storyId=45517
"--  Northwest Airlines - Reduced its schedule by 20 percent
--  Delta Air Lines - Reduced its schedule by 20 percent
--  Aer Lingus - Reduced its operations by 25 percent
--  AirTran - Reduced its schedule by 20 percent (...)"

----

Southwest
http://www.iflyswa.com/about_swa/press/prindex.html

Sept. 11 - Southwest Airlines reports "that all Southwest flights are
currently safe and on the ground (...) Southwest will not operate
scheduled flights for the remainder of the day."

Sept. 12 - Southwest Airlines "confirmed that it will not resume
scheduled service again tomorrow."

Sept. 13 - Southwest Airlines"announced today that it will resume
scheduled service at 11 a.m. Central Time on Friday, Sept. 14."

Sept. 17 - Southwest Airlines "yesterday operated approximately 98
percent of its normal Sunday flight schedule, with 97.6 percent of
those flights operating ontime."

----

Frontier
http://www.frontierairlines.com/news/newsIndex.asp?section=general&year=2001

Sept. 11 - Frontier Airlines "reports that all Frontier aircraft are
accounted for and are on the ground as of 10:15 a.m. MDT. Effective
immediately, the airline has suspended operations for the remainder of
today (...)"

Sept. 13 - Frontier Airlines "will resume partial flight service today
at 12:45 p.m. MDT (2:45 p.m. EDT). At that time, the airline will also
complete two flights destined for Denver, which were diverted to
Detroit and Toronto due to the ground stop on Sept. 11."

Sept. 18 - Frontier Airlines "announced it would cut its flight
schedule, effective Oct. 1. 2001, by approximately 20 percent."

Sept. 20 - Frontier Airlines "today announced it has resumed
approximately 80 percent of its flight schedule, and is operating at
an approximate 90 percent on-time rate."

----

I hope this helps!