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[ED STATES TMENT OF MERCE

ICATION NBS TECHNICAL NOTE 568

Simulation of Air Traffic

Control Radar Beacon Code

Assignment Plans

Final Report

HAL BUREM! Of STMWKS

[09

1/

3. ,

UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

/ 1 S NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

NBS TECHNICAL NOTE 568

ISSUED MARCH 1971

Nat. Bur. Stand. (U.S.), Tech. Note 568, 76 pages (Mar. 1971)

CODEN: NBTNA

Simulation of Air Traffic Control

Radar Beacon Code Assignment Plans

Final Report

R. D. Elbourn

Information Processing Technology Division

Center for Computer Sciences and Technology

and

Judith F. Gilsinn

Operations Research Section

Applied Mathematics Division

National Bureau of Standards

Washington, D.C. 20234

Sponsored by the Department of Transportation

Federal Aviation Administration

Inter-agency Agreement D0T-FA69WAI-162

*"»«„ of *

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

(Order by SD Catalog No. C 13.46:568). Price 70 cents Stock Number 0303-0847

CONTENTS

PAGE

1. Introduction. ......... ........ 1

2. The Simulation Model 4

3. Traffic Statistics 8

4. Center Assignment Plan 11

5. Master Assignment Plan. . ......... 23

6. Airline Assignment Plan 29

7. Altitude Strata Assignment Plan . 33

8. Directional Assignment Plan 35

9. Fixed Code Assignment Plan. ....... 36

10. Summary 37

Appendix A. Center- to-Center Flight Model 41

Appendix B. On Simulation Strategies and Simulation

Programming Languages. ..... 47

Appendix C. Traffic Flow Data 51

LIST OF FIGURES

Figure 1. Duration of inter-center flights. ......... 12

Figure 2. Duration of flights within the same center. . , . . 13

Figure 3. Regional airlines that could share a code bank. . . 31

Figure 4. Route map between the 21 airports ......... 40

iii
LIST OF TABLES

PAGE

Table 1. Operations by centers ..:....... 9

Table 2. Number of aircraft with beacon codes in each center

on the hour ............... 10

Table 3. Maximum number of aircraft with beacon codes in each

center during each hour .............. 10

Table 4. Distribution of duration of flights . 14

Table 5. Three center assignment plans ........... 14

Table 6. Center assignment plan with 700 codes for intercenter flights assigned by random selection .... 18

Table .7. Master assignment plan with codes returned at

each handoff 26

Table 8. Master assignment plan with codes returned only at

arrival ...................... 27

Table 9. Flights of regional airlines in the 21 centers . . 28

Table 10. Use of same centers by regional airlines 30

Table 11. Comparison of code assignment plans 38

Table 12. Analysis of local flights 44

Table 13. Analysis of local flights ...... 45

Table 14. Analysis of local flights (concluded). ...... 46

Table 15. Departures from, arrivals at, and handoffs to each

center by hours. ................. 52

iv
Simulation of Air Traffic Control Radar

Beacon Code Assignment Plans

Final Report

R.D. Elbourn and J.F. Gils inn

In the Air Traffic Control Radar Beacon System

transponders in the aircraft use one of 4096 identity

codes when replying to interrogation from the

Secondary Surveillance Radar. Two types of plans

for assigning identity codes to aircraft were

tested by simulating in a digital computer a peak

day's IFR traffic in the USA. In one type each

Air Route Traffic Control Center assigns codes

independently of all the others, while in the other

type a single master center makes all the code

assignments for the USA. Four other types of plans

are discussed, and an assignment plan of mixed type

is proposed for further study. The strategy of

simulation and the use of the SBtSCRIPT language are discussed in an appendix.

Key words: Air traffic control; beacon code

assignment; digital simulation; radar beacon system.

1. Introduction

The primary, skin-reflection radar used for air traffic control

is supplemented by a Secondary Surveillance Radar or Air Traffic Control

Radar Beacon System (ATCRBS) , which employs radar beacon transponders

in the aircraft*, Interrogation from the ground by the proper signal

causes the transponder to reply with a special pulse sequence that is

one of 4096 discrete identification codes. If instrument flight rule

(IFR) traffic in the USA triples by 1980, as is predicted, there will

be many more aircraft flying IFR in the USA during a busy hour than

there are beacon codes. Thus arises the problem of how to assign codes

to aircraft so that the same code can be used simultaneously by

1
several aircraft in the USA, yet two aircraft using the same code will

not come into the same area and have their identities confused. This

report describes a study of various radar beacon code assignment plans

by using a digital computer to simulate their operation on a peak day's

IFR traffic in the USA.

For human recognition a beacon code is represented by four octal

digits in the range 0000 to 7777. A pilot can set his transponder

to any beacon code just by flipping four eight-position thumbwheels.

Nevertheless, it is desirable to minimize code changes in flight because

each change requires another controller-to-pilot communication, and there

is always a chance of turning to a wrong code.

By 1973 a computer-based semi-automatic system for air traffic

control is expected to be installed in most large and medium enroute

and terminal ATC facilities. In such a system a computer uses radar

data to track each aircraft under control and files the data on each

aircraft under a unique track number. The beacon code that accompanies

a secondary radar reply is not normally of concern to the controller,

but is used by the computer to find directly the number of the track that

should be updated.

To appreciate how much computer work the beacon code saves, one

might recall that the largest single task of the computers in the SAGE

air defense system was correlating new radar returns with the proper

tracks. Now what happens to this system if two aircraft with different

track numbers have the same beacon code? The computer may start to

update the wrong track, but the new position coordinates will usually

be so different from the old that it will be apparent that this
is the wrong track, and the computer should look for another track

having the same beacon code. Only when the two tracks cross in nearly

the same position should identity be in danger of interchange. However,

because there is some burden on the computer in rejecting wrong correlations, all the code assignment plans considered in this study have

incorporated the conservative rule that no two aircraft may use the

same beacon code within the area controlled by one Air Route Traffic

Control Center (ARTCC) . This rule keeps beacon codes as well as track

numbers unique within the area served by a single computer.

This computer may receive data from a radar that is sited near

the boundary between two control areas, so. that it looks into both

areas. Such a radar may well see two aircraft, one in each area,

with the same beacon code. We assume that in this case the computer

will use the geographical separation of the targets. to decide as

described above which radar return comes from the aircraft it is

tracking.

Code plans in this study are all intended for use in the semiautomatic system. In Section 7 there is some discussion of compatibility

with the present 64-code manual system, but these two systems use

codes for completely different purposes. In the manual system beacon

codes permit the selective display of targets by classes such as

arriving aircraft, departing aircraft, or aircraft in the high altitude

sector. They are not used for individual identity. The semi-automatic

system does not need to get this classification information from the

beacon code; it has the information in the computer's file record and

incorporates it in the alphanumeric display.
Another rule, adopted for all simulations after the initial phase

of this study, is that beacon codes are assigned to flights 30 minutes

before departure* This, however, is an adjustable parameter in the

computer programs a

2„ The Simulation Model

The problem of generating a representative sample of air traffic

for testing a code plan was solved by the FAA's giving to NBS in April

1969 a magnetic tape called a Peak Day's IFR Traffic Tape for the USA.

This tape describes 31,598 flights by giving the following flight plan

data on each:

1, Aircraft identity

2. User class; i.e.

Air carrier

General aviation, or

Military

3« Aircraft type

4. True airspeed

5* Departure airport

6. Flying altitude

7. Destination airport

8. Departure time

Notice that in this usage a flight lasts only from take-off to

landing. The continuation after an intermediate stop is another flight.

Because we ao not have a peak day traffic tape for the projected

traffic of 198U, the 1969 traffic is used, but code assignment

plans are sought that will work with many fewer than 4096 codes,
in fact fewer than 1000. It will be shown that the plans we simulate

require a number of codes proportional to the traffic served; hence

this policy leaves room for at least a three times increase in traffic

as well as the reservation of some codes by the military. The ratio of

the number of aircraft served to the number of codes used is an important measure of goodness in an assignment plan.

Instead of describing the complete airways structure of the USA

within the simulation model and routing the flights via the airways, it

was considered adequate to use straight line flight paths from the

departure airport to the destination airport. Rather than true great

circles the paths of simulated flight are straight lines on a flat

map. The map projection is Lambert Conformal Conic with standard

parallels at 33° and 45° north latitude. Thus it became necessary to

look up the latitude and longitude of each airport mentioned on the

Peak Day Tape and to convert these into x, y map coordinates. Places

were omitted in the following circumstances:

1„ The identifier recorded on the tape was not in the list of

location identifiers.

2. The airport was outside the contiguous 48 states.

3« The location was an airways intersection rather than an

airport.

4, The airport was not listed in either the IFR-or VFR- Supplements

(DOD Flight Information Publication (Enroute)).

5. The airport was not on a list supplied by the FAA and had

fewer than 10 operations on the Peak Day Tape.
The result was a list of 1113 airports and 27,692 flights between these

airports o These flights were recorded on the exogenous events tapes

used to drive the simulation programs. International flights are not

included but in comparison with domestic flights their volume is small.

At the start of the simulated day there should be a representative

number of flights already in progress, otherwise it would take several

hours for traffic to build up to its proper density, and during these

early hours there would be too few handoffs between control centers and

too few arrivals at destinations. The end of the simulated day occurs

at the same hour as the beginning, so the most obvious solution is to

record the status of those flights in progress at the end of the day,

make their times 24 hours earlier, and preload them into the system as

flights in progress at the start of the day. Thus the events of a

simulated day are treated as one complete cycle of a daily recurring

sequence.

Since the Peak Day Tape gives only the departure time of a flight,

the times of arrival at subsequent points are computed by using as

ground speed the value reported for true airspeed. In a few cases this

value is zero, so 500 knots is used instead. When the destination of the

flight is the same airport from which it departed, a duration of one

hour is assumed.

The boundaries of the control areas of the 21 ARTCC's are described

to the computer by the coordinates of about 300 corner points. Latitudes

and longitudes of the corners were scaled from the enroute high altitude

US jet route wall planning charts of 3 April 1969 and were converted to

x, y map coordinates. The problem of finding where a path of flight

"6
crosses the boundary of a center is solved as follows,, A new system

of x, y coordinates is defined by shifting the origin of coordinates to

the departure airport and rotating the axes until the positive x-axis

points to the destination airport,, The new y-coordinate of a point is

thus its distance (positive to the left) from the path of flight. Given

that the flight is in center area A, the new y-coordinate of each

boundary point of A is computed point-by-point around the boundary in

clockwise sequence. If two successive boundary points have new y-coordinates with opposite signs, then they lie on opposite sides of the flight

path, so the path crosses the linear boundary segment between them. The

crossing point is then easily computed. Because the shapes of the

center boundaries are not necessarily convex, a straight path of

flight may cross the boundary of one center 2,4, or more times. All

crossings are found, but only the nearest one in the forward direction

of flight is retained. The time of arrival at this point becomes the

time of handoff to the next center. Of course, if the destination

airport is nearer than the nearest boundary crossing ahead, then the

flight will terminate without another handoff.

The curious irregularities of some center boundaries were doubtless

introduced to put the crossings of busy airways in convenient places,

but they introduce some adventitious crossings of the straight- line

flight paths. For example, the line from New York's Kennedy Airport -to

Los Angeles International crosses from Indianapolis Center into Chicago,

back into Indianapolis, and again into Chicago before reaching Kansas

City.
3„ Traffic Statistics

Before any code assignment plans were simulated, some runs were

made to get statistics on how the traffic sample is distributed in time

and space,, Table 1 shows the number of departures from, handoffs to,

and arrivals at each center area during the 24 hours. Appendix C

gives for each center area and for each hour of the day the number of

departures to each center area, the number of arrivals from each

center area, and the number of handoffs from each adjacent center.

There are many small discrepancies on the order of 10 units between

these data and corresponding data obtained later from the code plan

simulation runs. These may be the result of taking the hourly data

summaries about 3 seconds later in the flight statistics runs. Whatever their cause the discrepancies are much too small to affect any

conclusions; therefore repeating runs in an attempt to get exact

agreement was not considered worthwhile.

Table 2 shows the number of aircraft with beacon codes in each

center on each hour during the day. The numbers include those

aircraft that have been given a code because they will depart within

a half hour. The total number of codes in use in the USA reached

2593 at both 20:00 and 21:00 GMT, while the number in the Chicago center

reached 244 at 24:00 GMT. The maximum numbers of codes required

will in general be reached within rather than on the hours. These

maxima are given in Table 3. Chicago center needed 260 codes sometime

between 23:00 and 24:00 GMT. Canada appears as a center because some

straight-line flights between points in the USA pass over Ontario,

although no flights originating or terminating in Canada were included»

8
Table 1. Operations by centers

Center Departures Handoffs Arrivals

from to at

Albuquerque 717 811 769

At lanta 1688 1609 1651

Boston 1619 687 1434

Chicago 2701 2227 2746

Cleveland 2413 2753 2302

Denver 614 1058 601

Fort Worth 1675 1294 1674

Great Falls 265 155 276

Houston 1638 67.1 1592

Indianapolis 1520 1947 1474

Jacksonville 1162 1358 1108

Kansas City 1276 1262 1318

Los Angeles 1783 874 1764

Memphis 757 1228 826

Miami 905 463 884

Minneapolis 777 423 759

New York 2064 2596 2571

Oakland 1131 617 1168

Salt Lake City 301 502 305

Seattle 748 177 702

Washington 1938 1563 1768

Totals 27692 24261 27692
Table 2. Number of aircraft with beacon codes in each

center on the hour

AT GMT 1 2 3 4 5 6 7 8 9 in 11 12 13 14 15 16 17 18 19 20 21 22 23 24 CENTER BOSTON 54 49 45 25 13 9 6 9 3 14 75 94 99 109 108 96 90 102 118 110 104 93 90 71 NEW YOKK 100 89 51 46 51 28 13 8 16 18 84 155 167 189 174 151 141 140 151 169 159 156 156 120 WASHINGTON 112 71 5fi 19 28 19 7 11 7 24 47 117 164 190 174 167 157 149 184 161 146 135 129 128 JACKSONVILLE 75 60 46 46 21 13 13 8 11 13 H 34 59 138 134 116 132 116 148 145 143 131 122 113 MIAMI 31 39 52 32 20 17 9 8 7 4 18 37 76 87 59 66 64 85 95 78 80 76 58 60 CANADA 2 3 1 n 1 n 2 2 3 5 2 4 4 2 1 CLEVELhND 112 102 64 66 46 28 25 29 20 31 PI 173 194 2(15 193 158 159 2(13 217 210 202 185 168 140 ATLANTA 123 92 54 51 42 20 13 10 16 14 18 51 111 115 122 137 155 156 159 172 167 172 141 139 INuIANaPOLIS 10b 70 57 43 36 17 18 4 9 22 16 60 124 148 146 128 129 130 112 172 182 157 147 135 CMICAGu 171 143 103 141 64 35 29 39 31 31 25 51 148 189 215 189 186 207 200 227 201 233 233 244 MEMPHIb 52 51 39 24 23 9' 11 7 4 6 14 39 61 85 100 96 95 PO 84 90 102 87 90 61 HOUSTON 91 60 64 45 34 14 7 11 4 4 5 14 52 125 146 174 166 165 139 166 157 163 156 130 MINNEAPOLIS 30 23 32 17 11 8 8 4 6 8 19 39 78 62 59 58 68 61 69 53 49 51 59 58 KANSAS CITY lu6 64 67 46 39 31 15 25 27 15 8 23 62 118 124 118 106 128 131 133 161 136 145 108 FORT WuRTH 100 79 46 45 30 22 18 20 11 9 17 58 117 133 167 204 175 192 197 207 202 186 165 129 GREAT FALLS 12 12 8 10 54 53 15 31 28 19 19 6 3 5 10 17 22 24 11 12 20 24 10 14 DENVER H7 68 53 40 24 29 23 27 35 19 11 15 29 49 50 81 95 120 83 78 86 84 84 97

ALtSUQUtRQUE 60 63 58 43 35 21 22 19 14 14 11 8 11 27 79 106 101 94 97 99 122 120 93 90 SALT LAKE CY 34 39 29 24 24 11 9 12 6 11 12 5 4 7 25 36 57 48 46 36 47 41 37 39 SEATTLE 36 39 39 25 23 25 21 24 35 25 21 19 17 33 52 60 57 49 51 47 36 44 52 46 OAKLANj 77 91 63 56 42 36 25 13 8 11 4 6 18 52 93 1 14 126 86 91 85 77 71 84 96 LOS ANGELES 153: 111 97 8? 79 62 55 34 20 24 13 14 16 32 74 122 136 148 130 141 150 118 129 137 172414181125 926 739 507 362 354 318 337 52610181612210023(17239924192487251725932593246323482156

!

Table 3. Maximum number of aircraft with beacon codes

in each center during each hour

11 12 13 14 15 16 17 18 19 20 21 22 23 24 CENTER MAXIMUM BOSTON 75 59 57 46 25 14 14 9 9 14 77 97 104 115 116 110 100 116. 122 132 116 115 100 92 132 NEW YORK 120 110 91 56 53 51 29 16 17 IP 84 169 175 192 196 179 164 141 163 179 191 165 163 161 196 WASHINGTON 142 112 77 59 40 30 19 14 13 24 TT 119 168 193 190 185 167 165 187 190 182 153 151 139 193 JACKSONVILLE 116 76 60 53 51 28 13 15 11 14 13 35 62 138 150 138 137 140 154 181 147 162 132 126 181 MIAMI 61 41 53 53 32 20 18 10 9 7 18 39 76 89 91 70 67 91 104 95 87 84 77 65 104 CANADA 4 4 4 1 1 1 1 2 1 1 3 2 6 6 5 5 5 7 6 3 2 7 7 7 CLEVELAND 153 126 104 67 75 50 29 34 32 31 81 185 198 iii 205 196 170 209 217 218 212 205 198 173 218 ATLANTA 145 131 92 66 53 47 21 13 18 20 18 60 112 127 132 154 169 168 164 174 179 203 180 156 203 INDIANmPOLIS 139 111 79 60 61 36 27 21 11 23 24 61 125 155 170 149 135 135 142 174 183 189 169 152 189 CHICAGO 247 171 1.43 144 141 67 37 43 Si, 38 34 52 153 192 SM 225. 208 21_3. 207 237 235 237 240 260, 260 MEMPHIb 71 55 51 39 28 27 12 1 1 7 7 14 39 61 85 1(16 102 107 98 92 107 107 97 96 107

HOOSTOi. 130 93 69 64 47 34 16 11 13 7- 8 14 52 125 165 174 192 176 176 167 171 172 176 158 192 MINNEAPOLIS 58 34 34 36 17 12 9 a 6 8 19 39 78 81 65 66 75 75 72 74 57 56 66 61 81 KANSAS CITY 121 113 79 76 46 40 31 28 27 29 16 24 63 122 135 137 124 129 139 148 165 170 147 146 170 FORT WuRTH 130 100 84 55 49 33 22 26 20 11 21 60 U7 141 168 206 209 193 206 208 228 209 186 166 228 GREAT FALLS 18 14 13 14 54 57 53 32 35 30 22 19 10 7 12 18 23 24 25 12 23 25 24 16 57 DENVER lua 90 69 57 40 29 29 27 42 35 21 15 29 53 54 83 101 124 120 85 98 97 89 98 124 ALBUQUtRQUE 90 69 73 58 45 35 29 24 21 17 18 11 15 27 79 115 113 ln4 104 100 122 133 120 96 133 SALT LAKE CY 47 39 41 29 29 24 15 15 12 11 16 12 4 9 26 37 57 61 52 46 48 58 48 40 61 SEATTLE 52 53 39 41 32 25 25 26 37 37 30 25 22 35 54 63 72 67 51 57 51 47 54 54 72 OAKLANu 97 91 101 66 58 47 36 27 13 13 11 6 18 53 93 1 18 126 127 91 93 85 80 86 103 127 LOS ANGELES lbU 153 119 105 84 83 63_ ts~ 35 31 26 18 20 32 79 127 139 159 150 150 179 152 131 139 179 MAXIMUM 247 171 143 144 141 83 63 60 43 38 84 185 198 214 230 229 209 213 217 237 235 237 240 260 260
To study the utilization times of codes one wants data on the

distribution of the durations of flights. Flights that originate and

terminate at the same airport are a special class, because they have

been arbitrarily assigned a duration of one hour. In some code plans

it is desirable to treat flights that originate and terminate in

the same center area differently from flights that must be handed off

because they originate and terminate in different center areas. For

these two classes flights were tabulated by 10-minute intervals of

duration from zero to 480 minutes. Figures 1 and 2 show the cumulative

distribution curves for these two classes plotted with a normal

probability scale for the cumulative percentage of flights and a

logarithmic scale for the duration of flight. The near linearity of

these curves shows that the distributions are approximately log-normal.

Unfortunately 10 minutes is too long an interval to describe well the

shorter flights within a single center area, but the only substantial

departure from log-normality is that the flights within a single center

area have too few flights of 120 minutes or longer duration. The flights

that return to the same airport are counted here as having zero duration.

Table 4 gives the means and some selected percentile points for these

distributions.

4. Center Assignment Plan

In a center assignment plan each ARTCC has available to it the

complete set of radar beacon codes. It keeps a record of which codes

are in use within its control area, and it issues each originating

flight an unused code. A flight coming into a center's control area

from outside may retain its code if this code -is not in use in

this area. Otherwise its code is changed to an unused one. Thus

11
10 99.9

99.8 -

99.5 —

99 —

98

0.5

FLIGHT DURATION-MINUTES ( LOGARITHMIC SCALE)

20 30 40 50 60 90 120 180 240 360 480

BASED UPON 14,198 FLIGHTS

AIRPORT -TO -AIRPORT MODEL --- CENTER -TO -CENTER MODEL

(SEE APPENDIX A )

1.0 1.5 2.0

LOG |0 (FLIGHT DURATION)

2.5

FIGURE 1. .Duration of inter-center flights

12"
FLIGHT DURATION-MINUTES

10 20 30 40 50 60 90 120 99.99 1 1 1 1 1 1

1 1 1 1 1 1 1 J

99.95 -

99.9 - -

99.8 BASED UPON 13,496 FLIGHTS -

99.5 -

CO

LU 99 _

J—=>

21* 98 — — X

z-X. K—Of 95 —LU

ce

<=> 3=CO

90 — —

CO

I

3TCO

1 u_

u_ 80 — —

1

2:

70 —

LU

O60

50

40

30

20 1

1 1 1 1

1.0 1.5 2.0

LOG

|

(FLIGHT DURATION)

FIGURE 2. Duration of flights within the same center

13 .
Table 4. Distribution of duration of flights

Within Between

one different

center, centers,

minutes minutes

Means

20 68

Percentiles:

1 10

10 20

25 8 30

50 16 50

75 27 77

90 40 139

99 81 275

No. of Flights 13,496 14,198

Table 5. Three center assignment plans,

25,646 flights, 800 codes

Issue Issue Issue by

from top, from top random

return to return to selection

bottom top

Handof fs 18,986 18,986 18,986

Code changes 3,200 10,976 2,469

Percent changes 17% 58% 13%

14
each center prevents duplication of codes within its control area,

but use of the same code in different contro]. areas is freely permitted.

There is no communication between centers to reserve codes for extended

f lights,,

The first suggestion for a center assignment plan required each

center to keep a list of its codes that are not in use, to issue codes

from the top of the list, and to return them to the bottom An alternative is to return codes to the top of the list. In the preliminary

phase of this project both these plans were simulated using a simplified

model of air traffic movements that is described in Appendix A of this

report. But neither plan performed as well as a third plan in which

codes were issued in random sequence. The comparative results when

800 codes were available to each center are shown in Table 5.

At the start of simulation all 21 code lists were in the natural

sequence 1, 2, 3, Because all centers began issuing the same

codes, the probability of code conflict at handoff was high. When

codes were returned to the bottoms of the lists, the code lists

gradually became randomly shuffled so that performance tended toward

that of the random plan.' However, when codes were returned to the tops

of the lists, no center could get further into its list than the maximum

number of codes in use at one time. Most of each list was never used,

and all centers continued using only the lowest numbered codes, so

conflicts were frequent.

15
Another disadvantage of both plans that issue codes from a list or

stack is that their implementation requires an excessive amount of

computer memory. For 800 codes and 21 centers they require (800) (21) =

16,800 words. Each word contains two addresses, one pointing to the preceding code in the stack and one pointing to the succeeding code. An

attempt to run the simulation with 1100 codes aborted with memory overflow.

The random assignment plan needs only one bit for each code and each

center to tell whether or not that code is in use in that center.

The idea behind the better-working random assignment plan is the

following. Consider one aircraft coming into a new center. One wishes

to minimize the probability that its code is in use in this center.

But if the center had no prior knowledge of which particular code this

aircraft is using, it could do no better than to make the probability

of use equally small for all codes. In other words the codes in use

should be randomly scattered throughout the space of available codes.

When a code is needed, the computer makes a random draw from the whole

complement of available codes by invoking a pseudo-random number

generating routine. If this code is in use, another is drawn until

an unused code is obtained.

Reflection on this plan suggested a further improvement. Recall

that the traffic sample divides about equally between local flights

that do not leave the center area in which they originate and nonlocal

flights that terminate in other centers. The local flights can be

served without any code conflicts at all if each center uses the same

bank of only about 100 codes for them. The remaining, say 700, codes

can then be used in the random assignment plan for the nonlocal flights.

16
Because there are almost as many codes available for many fewer flights,

many fewer code changes will be required.

The particular code assigned to a local flight never has any effect

in the simulation; therefore the program does not assign any codes to

local flights. Instead it counts the number of local flights in progress

(including those that will start within one-half hour) in order to

learn how large a code bank, needs to be reserved for local flights,,

Table 6 shows the hour-by-hour and center-by- center results of

simulating the center assignment plan using 700 codes for the

nonlocal flights and issuing codes one-half hour before departure.

The overall summary results are:

Handoffs 24,261

Actual codes changed 2,370

percentage 9.76%

Expected code changes 2,727

percentage 11.08%

Most local flights in one center 116

The numbers of code changes that actually occur are random

variables. They are sums of the code changes that occur on individual

handoffs and each of these depends on the particular "deal" of the random

code assignments. At a particular handoff let n be the random variable

that equals 1 if a code change is required and equals if a change is

not required. If p is the probability that a code change will be

required, then the expectation value of n is

E(n) = 1-p + O.(l-p) = p,

17
Table 6. Center assignment plan with 700 codes for inter-center

flights assigned by random selection (3 pages)

10 11 12 13 in i9 2n 22 23 ?4 TOTAL

ALBujUEROUE

HmNOOFFS to ACTUAL CODE CHANGES EaPecteu cone changes LuCAL flights

ATLANTA HaNOOFFS TO ACTUAL CODE CHANGLS

EaPECTEU CODE CHANGES

LuCAL FLIGHTS BOSTON

HrtNDOFFS TO actual code changes EaPecteu code changes

luCal flights

CHICAGO

h..ndoffs to actual code changes

expected code changes

LoCAL flights cleveland

h*.nuuffs to actual cooe changts

EaPECTEU CODE CHANGES

luCAL FLIGHTS

DENVER HANDOFFS TO ACTUAL CODE CHANGES

EXPECTED CODE CHANGES

LuCAL FLIGHTS

FORI WORTH

HANDOFFS TO ACTUAL CODE CHANGES

EaPECTEu CODE CHANGES

LoCAL FLIGHTS

3KE-*T FALLS

HaNDOFFS TO ACTUAL CODE CHANGES EaPECTEN COOE CHANGES LuCAL FLIGHTS

HOUSTON HmJUUFFS TO actual code changes

EaPecteu code changes

ljcal flights

indianapolis HmhDOFFS TO 119 ACTUAL CODE CHANGES 14 EaPECTEO COOE CHANGES 15 LOCAL FLIGHTS 42

54 33 33 35 25 12 20 11

10 19 19 13

110 55 33 60 50 23 15 ll 12

41 39 37 25 14

3b 39 30 14 13 13

42 26 34 27 12

67 57 57 39

8b 59 53 62 63 24

18b 130 91 71 77 47 24

39 35 26 22 19 14 12

71 63 51 45 30 30

34 32 lb 10

35 27 16 la

65 49 40 35 23 11

JACrvSONVILLE

Hf.NuOFFS TO ACTUAL CODE CHANGES

EaPECTEU CODE CHANGES

LC-CAL FLIGHTS

KANSAS CITY

rii.iJDOFFS TO ACTUAL CODE CHANGES

EaPECTEU CODE CHANGES

LOCAL FLIGHTS

LOS ANGELES

I-W4DOFFS TO ACTUAL CODE CHANGES

EaPECTEU coul CHANGES

LOCAL FLIGHTS MEMPHIS

HmNDOFFS TO

ACTUAL CODE CHANGES EXPECTED COOE CHANGES

LuCAL FLIGHTS

MIAmI HANDOFFS TO ACTUAL CODE CHANGES EaPECTEU CODE CHANGES

LOCAL FLIGHTS MINNEAPOLIS

HhNDOFFS to actual code changes

EXPECTED CODE CHAuGES

LuCAL FLIGHTS

NE* YOKK HANDOFFS TO ACTUAL CODE CHANGES

EXPECTED COOE CHANGES

LOCAL FLIGHTS

OAKLAND

H/.NDOFFS TO ACTUAL CODE CHANGES EaPECTEU CODE CHANGES

local flights

salt lake cy handoffs to actual code changes expected code changes

local flights

SEATTLE HaNDOFFS TO actual coue changes

expected code changes

local flights

WASmIngTON

H/.UUOFFS TO ACTUAL COOE CHANGES EaPECTED CODE CHANGES luC^ flights

75 54 49 62 36 25 11

31 23 16 10

75 54 64

37 32 26 2b 17 11 10 10

81 65 42 50 34 25 20 20 12

64 59 50 i*8 38 38 2b

67 63 37 32 35 22 12

36 25 31 IB 12 18

20 13 10

22 19 23 17 14

19 12 12 15 12

19 26 44 50 46 61 57 57

13 39 62 56 38 35 37 4fi 50 44 37

16 54 96 110 86 90 103 91 132 102 130 102 109

50 51 51 29 31 27

72 62 34 6b 39 24 16 16 33

14 20 17

11 10 10 24 IP 19 13 15

11 12 11 15 15 12 20 17 24 15 15 45 49 50 US 57 59 61 58 61 57 54

28 27 47 35 37 35 4? 48 46 35 35 53

39 43 38 61 62 58

1 8 13 17 12 15 15 53 66 57

11 2? 58 85 64 88

15 17 26 25

10 16 10

bl 64 57 59 56

11 25 68 73 .82 69 80 87 71 8?

25 49 61 57 53 56

22 2? 59 41 33 35 37 37

126 127 R5 52 57 37 18 18 29 15 33 104 148 158 143 150 1 52 116 148

11 15 10 14 14 7 2 3 29 22 21 20 10

38 65 47 37 28 32 15 11

32 30 17

37 25 25 25 18

15 10 12

20 28 18 26 19 ,6 28

1 14 26 28 24 24 23 14 25

34 45 40 64 66 63 52 42 39 39 42 35 27 33

12 lfi 34 38 23 39 30 38

35 41 57 76 70 46 51 42 30 33 43

21 32 56 42 25 18 22 37 35 24

20 20 22 17 15

10 17 15

31 32 24 19 17 17 16 21 31 32 25 22 15 25 35 33 38 34 40 31 27 25 29

112 50 52 30 52 20

3b 2b 22

11 32 , 72 94

37 36 81

1608

183 202

60 67 66 54 50 53 45

78 112 122 108 128 j 49 133 l 54 ]25 149 149 1 64 2228

9 15 13 15 20 16 30 26 19 29, 22 31 316

6 15 19 17 21 26 25 32 2? 27 28 34 339

21 90 109 102 85 82 74 86 86 98 98 99

26 66 138 155 132 141 148 155 157 ]9o 20O 187 i93 178 2762

1 3 17 24 19 18 21 21 22 35 27 29 29 17 339

1 9 24 30 2U 25 24 28 30 35 38 35 35 28 429

31 67 61 62 67 68 52 67 74 68 59 67 51 40

13 16 60 82 83 71 59 59 72 68 67 1058

24 28 26 24 22 26 21 20 21

13200429 11 12 32 58 81 93 86 85 84

11 57 10

1 3 6 10 12 12 12 10

5 29 28 80 90 111 116 87 108 106 115 99 82 65

11 18 12

93 109 111 97 129U

9 18 13 11 116

14 17 16 13 146

18 26 30 37 54 38 57 51 42 50 54 49

72 96 101 115 115 107 96 98 98 102 84

23 123 134 1935

19 17 20 214

21 20 20 242

55 56 53

09 91 81 1358

lfl 11 6 130 17 11 10 143 16 35 33

78 104 S9 1262

7 12 8 118

9 13 11 122

55 54 54 64 73 58 45

51 43 45

22 42 67 S9 81 81 61 87 77 62 67

33 58 79 81 9l 89 83 73 101 67 90 74 1228

24 24 25 29 27 26 26 20 24 25 29 20 17

20 34 32 28 33 34 26 28 20 32

15 31 30 45 42 33 33 34 37 32 34 29 27 18

13 35 27 25 31 30 20 24 24 27 30

27 28 36 35

83 195 1714 168 164 2600 25 29 25 29 28 335

33 37 32 31 27 384

77 U8 87 75 110 105 113 102 102 100 1555

10 20 10 11 19 6 19 19 6 5 183

11 18 12 11 16 17 17 14 16 13 197 86 79 58 59 77 69 62 56 35 39
and the variance of n is

3 = E(n-p) 2 = (l-p) 2 p+(0-p)

2 (l-p) = p(l-p).

When independent random variables are added, their expected values

and variances are additive; therefore, if i denotes the i-th handoff,

the expected number of code changes is

E(Sni) = Epi,

and the variance of the number of code changes is

s = SPi(l-pi).

If the p^ tend to be about 0.1, then the factors (1-p^) are about 0,9,

so the variance- is about 0.9 times the expected number, and the

standard deviation is about 0.95 times the square root of the expected

number* Thus, if the number of code changes expected in a particular

center during a particular hour is 4 one should not be at all surprised

to actually observe any number in the range 4±2,

Because the sampling variations are so large, one would like to

obtain from the simulation some more stable estimate of the number

of code changes to expect. If the codes in use in a center are distributed independently of the code of an incoming aircraft, then the

probability that a code change will be required yd just

A

P =

C

where A is the number of codes ( in use in the center and C is number

of codes in the code bank. Probabilities computed in this way were

accumulated to obtain the numbers called "expected code changes" in the

tables of results. The numbers of actual code changes are almost

always smaller than the "expected code changes" and the total of the

actual code changes, 2370, is less than the expected 2727 by about 7 19
standard deviations* The thing that is wrong is the assumption that all

the codes in use in the center are distributed independently of the code

of the entering aircraft.

To see how the assumption of independence may fail to be satisfied,

consider a particular flight, say, UA411 entering the Chicago center

area from Cleveland. A few aircraft now in the Chicago center may have

been in the Cleveland center area while UA411 was there. The codes

of these aircraft are certainly not the same as UA411's code because

Cleveland would not allow a conflicting code assignment. The true

probability that UA411's code will have to be changed is

A-N ,.

P = W, (1)

where N is the number of aircraft with these nonindependently assigned

codes. Subtracting N from the numerator and denominator gives a smaller

probability of change. Unfortunately there is no practical way to know

the value of N at each handoff and so to compute the true expected numbers

of code changes. However, as a first approximation to removing the

erroneous bias, one can multiply each number reported under "expected

code changes" by the factor 2370/272*7 = 0.87.

If the traffic doubles in numbers and we wish to keep the same

probability of code change at each handoff, then eq. (1) shows that we

have to double the size of the code bank; i.e.

2A-2N A^N

P " 2C-2N ~ C-N.

Of course the total number of handoffs doubles, and the total number

of code changes doubles.

20
The following variation on the random assignment plan was

suggested with a view toward minimizing code changes in flight. It

uses 2800 codes for inter-center flights, divided into four banks of

700 codes eacho The four banks are assigned to centers like four colors

to a map; i«e., center areas with a common boundary use different

banks. Furthermore it is attempted to avoid repeating the same

bank along heavily traveled routes* If the banks are called A, B, C,

and D, they are assigned to centers as follows:

D Albuquerque C

A Atlanta B

A Boston D

A Chicago D

C Cleveland D

B Denver B

A Fort Worth B

C Great Falls A

B Houston D

B Indianapolis D

C Jacksonville

The device of using four banks assigned as above was compared by

simulation with the use of 2800 codes in a single bank* The results are

as follows:

Kansas City

Los Angeles

Memphis

Miami

Minneapolis

New York

Oakland

Salt Lake City

Seattle

Washington, D.C,

21
Total handoffs 24,261

Expected code changes 681

percent 2.80%

Actual code changes (1 bank) 507

percent 2.09%

Actual code changes (4 banks) 310

percent 1.28%

Ratio: 507/310 1.63

Thus it appears that there is an advantage of 1.6 times in the

use of four banks in non-adjacent assignments. However, one caution

should be noted: if traffic increases by three times, a busy center

will contain more than 700 flights in the peak hour. This may still

not exhaust the code bank if enough of these flights have codes in other

banks because they originated outside this center.

Let us discuss this problem a little further. At most 2618

aircraft have codes at one time, and only somewhat more than half of

these are flying between different centers, so 2800 codes are more

than enough to give each inter-center flight a unique code. Suppose

each center were given a unique code bank proportional to its busy

hour departures. Then at this level of traffic every inter-center

flight would get a unique code. But when the traffic becomes great

enough to exhaust some center's code bank, what code should it issue?

It could make a random selection from outside its own code bank, but it

just might select a code of its neighboring center into which the flight

is about to go. Clearly it would be better to use a code of some remote

center. Or better yet, it might consult the flight plan of this aircraft

22
and use a code from some center remote from any in which this aircraft

will fly. Randomization is not an optimum policy when it ignores

relevant information.

Now suppose traffic increases much further; say it reaches two

or three times the level that each center can accommodate from its

own code bank. Now no center really knows what codes any other

center is issuing. In this case the random assignment strategy

actually becomes optimum.

So at low traffic densities unique code banks are optimum and at

very high densities random selection is optimum. It is at

intermediate densities that an optimum procedure is complicated and

further study is needed.

5. Master Assignment Plan

In a master assignment plan one master control center assigns

radar beacon codes for all IFR flights in the United States. All

flight plans are sent to the master center, and this center is notified

of every handoff and every arrival so that it can update its file

of codes in use. With all this information the master center can

assign codes so that no two aircraft in the same ARTCC control area ever

have the same code. Thus no one is required to change his code "in

flight unless there is a diversion, or a flight plan is changed in flight.

By issuing the same code to different flights whenever they will

not enter the same center area, the master center can try to minimize

the number of codes required. The simulation to be described found

that 465 codes suffice for the 27,692 flights of the peak day's IFR

traffic.

23
The master center keeps track of which codes are in use in each

ARTCC. When a flight plan is filed, in this model 30 minutes before

departure, the master center first determines in which centers this

flight will fly. Then it finds the first code that is not in use

in any of these centers and reserves that code for the flight.

This- process is accomplished in the computer simulation by

reserving one computer word for each code. Within that word each center

has its own corresponding bit position in which a 1-bit signifies

that that code is in use in that center. When a flight is handed

off from a center or terminates in a center, the corresponding 1-bit

is reset to 0.

While analyzing a flight plan the computer generates a mask

word that contains a 1 in the bit position of every center in which

the flight will fly. It then uses this mask to test the memory words

of code number 1, then number 2, and so forth until it finds the

first word that has 0's everywhere that the mask has a 1. Each

of these 0's is changed to a 1, and the corresponding code is assigned

to the flight.

It may seem wasteful to reserve a code in Los Angeles 30

minutes before the flight will depart from New York, but in order to

let some other aircraft use that code in Los Angeles before the flight

from New York arrives, one would have to keep track of code reservations

by blocks of time. This would multiply the records that must be kept

by the number of time blocks used and would correspondingly increase

the time spent in searching them. The saving in codes that might result

does not seem worth the greater complication of the system.

24
Table 7 gives the results of simulating the master assignment

plan. The number of aircraft with codes reached 2618 in the hours

20:00 to 22:00 GMT, and the highest code in use reached 465, so on

the average each code was serving over 5 1/2 aircraft.

To achieve its virtues of no code changes in flight and great

economy in code use, the master assignment plan requires many

communications to the master center. It would save 24,261 messages

on the peak day if the master center were not notified of handoffs. A

code would then remain reserved in every center area that a flight flies

over until the flight ends. Table 8 shows that this scheme increases

the number of codes needed from 465 to 547, which seems a very modest

increase considering the communications saved.

One may now ask how many more codes are necessary if the level of

traffic doubles. Suppose that these added aircraft are called blue

aircraft and that they are served from a second code bank called

blue codes. Clearly the blue code bank will have to be the same size

as the original code bank, since it serves the same number of aircraft.

Thus the number of codes required is no more than twice the original

number. If the blue codes are appended to the end of the original

bank and the combined bank is treated as one, then when the computer is

seeking a code for a blue aircraft it will first scan the original codes,

and sometimes it will find one of them available. The increased scanning of the original codes will result in their being used more densely,

and so riot all the blue bank will be needed. However, it would require

additional simulation with a larger traffic sample to find how much

slower than linear is the growth of the number of codes required.

25
Table 7. Master assignment plan with codes

returned at each hand- off

Hour

Max imum dur ing . GMT On the hour preceding hour

Aircraft Highest Aircraft Highest

with code with code

1

codes in use codes in use

1694 463 2161 46*5

2 1397 463 1726 463

3 1105 459 1420 463

4 913 459 1126 459

5 732 326 926 459

6 502 326 740 326

7 358 326 507 326

8 354 326 380 326

9 318 233 360 326

10 329 165 332 233

11 512 165 521 165

12 1021 303 1040 303

13 1612 341 1612 341

14 2101 388 2101 388

15 2272 392 2328 392

16 2368 409 2454 409

17 2380 409 2480 409

18 2456 428 2485 428

19 2480 454 2547 454

20 2550 463 2599 463

21 2542 460 2618 463

22 2431 460 2618 460

23 2321 465 2465 465

24 2137 465 2350 465

26
Table 8. Master assignment plan with codes

returned only at arrival

Hour

Maximum during

GMT On the hour preceding hour

Aircraft Highest Aircraft Highest

with code with code

1

codes in use codes in use

1694 530 2161 545

2 1397 530 1726 530

3 1105 530 1420 530

4 913 530 1126 530

5 732 492 926 530

6 502 492 740 492

7 358 492 507 492

8 354 492 380 492

9 318 288 360 492

10 329 184 332 288

11 512 184 521 184

12 1021 327 1040 327

13 1612 395 1612 395

14 2101 454 2101 454

15 2272 470 2328 470

16 2368 485 2454 485

17 2380 491 2480 491

18 2456 510 2485 510

19 2480 529 2547 529

20 2550 537 2599 537

21 2542 547 2618 547

22 2431 545 2618 547

23 2321 545 2465 545

24 2137 545 2350 545

27
Table 9. Fligh ts of reg ional airl ines in th e 21 centers

iH

cfl U CD M=Many flights

F=Few flights

Blank=No flights

4-1 COCD ts

•H<

a

CD

00

CD iH<

u

Q) •H

4-1 co

u

COO

4-1

cu

4-1

5-i O

S3

u

N

O

4-1 o

e

CD •H

CI

5-i CU

4Jo

Cti

!>< CD H

COd

5-i H

Albuquerque F M M

Atlanta M M

Boston M M

Chicago M M M M F

Cleveland M M M F

Denver F M F F F

Fort Worth M F F M

Great Falls F M F

Hous ton M M

Indianapolis M M M

Jacksonville M M

Kansas City F M F M F

Los Angeles M F F

Memphis F M M M M M

Miami

Minneapolis F M M

New York M M F F

Oakland M

Salt Lake City M M

Seattle M

Washington M F F M

28
6. Airline Assignment Plan

"Basic Concept—-Each airline is allocated a block of codes which it

in turn assigns. Airlines whose routes do not -cross or overlap

may be allocated the same codes. Non air carrier aircraft will

be assigned codes by the FAA," from "Modeling Objectives Pertaining

to ATCRBS Code Utilization Model/' Project 150-534, October 11, 1968,

Federal Aviation Administration, Systems Research and Development

Service, Systems Analysis Division.

We take "whose routes do not cross or overlap" to mean "whose

routes do not enter the same center area." If such airlines are to be

found, they are surely among the regional air carriers. Inspection

of a route map for nine regional airlines yielded the data in Table 9.

The distinction between many and few flights in a center area is rather

subjective, but it was made in the- hope that special treatment of a

few connections such as Trans Texas from Albuquerque to Los Angeles

would eliminate a number of overlaps. In Table 10 an M is entered

between two airlines if there is any center area in which both have

many flights. An F is entered if in every center area in which both

have flights, one or the other has few flights. Finally a means

there is no center area in which both have flights. To see which

airlines may use the same code bank the data in Table 10 are transformed

into compatibility diagrams in Figure 3. Lines in Figure 3a connect

airlines that have between them in Table 10. Three airlines, Air

West, Mohawk, and Southern are connected in a triangle which indicates

that they can share the same code bank with no conflicts. But then

the remaining six airlines must each have its own code bank, because

29
Table 10. Use of same centers by regional airlines

rH

COU

u CO >> ti (0 u a u CD *-> C K

CO CD CD CJ c u CD

01 Xi •H M O CD H

[2 00 P & Xi M S x\ co

CD a cO u y> TJ 4-» G

U fH o XI U ca CD CCS •H rH u o O N •H O U

<! <J Pn S s o fU CO H

Air West M F F F

Allegheny M M M M M F F

Frontier M M M M M M M

Mohawk M M F F

North Central F M M M M F F F

Ozark F M M F M M M M

Piedmont M M F F M M M

Southern F M F M M M

Trans Texas F F M F M M M

M = Many flights

F = Few flights

= No flights

30
so

oz NC

la ) COMPATIBLE WITH NO CONFLICTING FLIGHTS

AW

OZ NC

lb) COMPATIBLE WITH FEW CONFLICTING FLIGHTS

FIGURE 3. Regional airlines that could share a code-bank

31
there is no compatible pair independent of the first three. Alternatively the same number of code banks, seven, will suffice if Air West

shares with Allegheny, Piedmont, or Southern, and Mohawk shares with

Frontier, Soutern (if Air West does not), or Trans Texas.

In Figure 3b airlines are connected if they have either a or an

F between them in Table 10. This diagrams the relaxed relationship

of "compatibility except for a few flights". If four airlines were

able to use the same code bank, they would be connected in a quadrilateral

complete with both diagonals, but there is no such configuration in

Figure 3b. There are nine triangles but every one contains Air West,

so only one group of three airlines can use the same code bank. After

choosing the three, one can find two independent pairs, then the

remaining two airlines must have their own code banks. Five code

banks are required in all. Alternatively four pairs and one singleton*

can be found.

32
Considering that this plan takes care of only nine of the airlines

and leaves both the other airlines and all of general and military

aviation to use other code banks, one sees that the search for

airlines that can use the same code bank is not very profitable.

A more promising approach is to preassign codes to all

scheduled airline flights. The algorithm used in the master assignment

plan, described in Section 5, could make these assignments with a nearly

minimal number of codes. The value found there, about 5 1/2 concurrent

flights per code, would probably be achieved, except that some

allowance must be made for delays. If most delays would be covered

by a 30 percent extension of the scheduled flight duration, then

about 30 percent more codes would be needed. To incorporate schedule

changes the preassignment algorithm should be rerun perhaps once a month.

Advantages of preassigning codes are the reduction of communications to

obtain and to release codes and the convenience of each scheduled

flight's using the same code every day. Newly scheduled flights and

flights that are excessively delayed can be assigned codes in the same

fashion as nonscheduled flights.

7. Altitude Strata Assignment Plan

"Basic Concept —Codes will be assigned on the basis of aircraft being

within certain altitude layers which may be compatible with the

64 code assignment scheme. In addition, certain codes will be

used for climb and descent indications." Ibid.

If altitudes are partitioned into layers and the code-banks are

partitioned in proportion to the populations in these layers, then

the center assignment plan or the master assignment plan will work just

33
as well in each layer as it does in the unpartitioned system. But

why do that? First, it does not save any codes because different

code banks must be used for different layers. Second, the semiautomatic system has other means to obtain and retain altitude information

and displays it right alongside the target symbol. Third, the 64-code

assignment scheme is not really compatible with this or with any

discrete code plan.

The 4096-code system uses the beacon code as a unique identifier

of an individual aircraft, whereas the 64-code system like its parent

the IFF system uses the code to signify membership in a class. The

decoder on the controller^ display can select for display any 10 out

of 64 classes defined by two of the four octal digits in the reply.

Because these classes are arrival, departure, high altitude sector, etc.,

an aircraft must necessarily change codes as it passes from one phase

of flight to another. During the interim when the semi-automatic

traffic control system with 4096-code capability is used in some

parts of the country, and the manual system with only 64-code capability

is used in others, it would seem simplest to accept a code change at

handoff from one system to the other.

To a limited extent the schemes can be superimposed. The other

two octal digits allow 64 discrete codes to be associated with each

code in the 64-code system. If there are no more than 64 aircraft

in an arrival, departure, or high altitude sector, then each can have

a discrete code. But what is the purpose of this unless the aircraft

are simultaneously under the surveillance of two observers, one with

4096-code capability and one with only 64? Sixty-four codes is hardly

34
a large enough number for feeding into a 4096-code system, and the

identity is changed on handoff , say, from departure to high altitude

sector. The two systems are just different enough to be incompatible.

8« Directional Assignment Plan

"Basic Concept—For example, north/south flights on the west coast,

midwest, and east could use the same codes since the flights will

not run together. In general, flights which do not share a common

center could use the same codes." Ibid.

The last sentence quoted is a basic objective of the algorithm

for the master assignment plan described in Section 5. Partitioning

the country into groups or tiers of centers will not make this plan

work, any better and may make it work a little worse by introducing

extra constraints. On the other hand partitioning can make the

random assignment plan work a little better.

Suppose the country is divided into n parts such that a fraction q

of the flights extends into more than one part while a fraction (l-q)/n

flies within each part. If the same ratio of codes to aircraft is to be

retained, a fraction q of the original codes is needed for the extended

flights and a fraction (l-q)/n for the local flights.

Two cases yield values:

fraction of original codes needed

n q q+(l-q)/n

2 1/3 2/3

3 1/2 2/3

It appears that for reasonable numbers the improvement is significant

but not spectacular because it is difficult to find divisions with n

large without having q large.

35
The directional corridors are hopefully such a division. But

in thinking about air traffic it is easy to think mostly about the

long nonstop flights such as New York to Los Angeles or Boston to

Miami. It is easy to forget that these are a very small fraction

of all the flights. Most flights are much shorter and may be more

randomly distributed in direction,, For this reason it may be better

to group centers into nearly round clumps rather than into long, narrow

strips. Because intuition is such a poor guide, it might be worthwhile

to count the flights on the peak-day tape that stay within several

different partitions of the centers. However, the results might be

changed considerably if the scheduled airline flights were taken out

by preas signing their codes.

In summary, one can study this plan further, but the results

will have a specialized applicability and the benefits will be limited.

9. Fixed Code Assignment Plan

"Basic Concept--Each air carrier aircraft receives a unique

code when it enters the commercial service. This code is not changed

no matter where the aircraft goes in CONUS. The remaining aircraft

are assigned codes under one of the other plans such as 'Center

Assignment'." Ibid.

The only question about this plan is whether it is feasible

to have so many codes reserved for this one purpose,, Projections of

the air carrier fleet are

1968 1980 1995

2452 3600 6700

Wallace L. Ashby, "Future demand for air traffic services,"

Proc.IEEE vol. 58, pp. 292-299; March 1970.

36
10. Summary

Simulations of two assignment plans for radar beacon codes

show that the 1969 level of IFR traffic in the USA can be served with

only 500 to 800 codes. With these plans the same grade of service

for twice as much traffic will require twice as many codes. The two

assignment plans are quite different because they satisfy very different

constraints in the code handling system. Neither plan is optimum in the

sense of giving the best performance possible under the constraints it

assumes, but each is rather simple and so establishes a level of

performance that can be achieved without much complication.

Table 11 gives comparative results for two variations of each

plan. The master assignment plan uses three or four communications

with the master canter per flight, but requires no code changes in flight

and uses the fewest codes. The center assignment plan uses no

communications with a master center but requires nearly one code

change for every ten handoffs when only 816 codes are used (116 codes

are for flights that stay within a single center's area). Using 2916

codes and in particular using different banks in adjacent centers

reduces the code changes to only one in 810 handoffs.

A good code assignment plan will probably incorporate features

from various simple plans. For example one might include the following:

1. Scheduled air carriers have codes preassigned by the algorithm

of the master assignment plan.

2. A single bank of about 100 codes is used by all centers for

flights that do not leave that center area.

37
C

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ti>, 38
3« The remaining codes are divided into unique banks allocated

to the different centers in proportion to their traffic.

4. The algorithm to be used when this unique bank is exhausted

is subject to further development, but for a start one

might try a random choice from the banks of those centers that

are not adjacent to the center issuing the code c

39
co

QJ rH

•He

•P

+J

COC

•H

CO

0)o

c

cd 4J

co

•-I P

CO 4JU

o

£1

c

(UB

Ctf XI

CUO

Pi

F>4
Appendix A

Center-to-Center Flight Model

At the start of this project, i.e. in Phase I, it was apparent

that quite a lot of clerical work would be necessary to put into machine

usable form the data required to simulate flights along straight paths

from airport to airport with handoff of control at each crossing of a

center boundary. One had to look up the latitude and longitude of each

airport and of each corner of a center's boundary then convert all these

into x, y coordinates in a suitable map projection. It was desired to

get preliminary simulation results on some assignment plans before all

this was done. The scheme invented for doing this is called the "centerto-center flight model".

In this model just one airport is assumed in each of the 21 air

route traffic control areas. All flights originating or terminating in

a control area are assumed to originate or terminate at this one airport.

Moreover all flights between adjacent control areas are assumed to follow

a straight line between their respective airports. Figure 4, a map

of the U.S., shows these 21 airports and the 44 paths between the airports

of adjacent centers. Longer flights are assumed to follow a shortest

path through this network. Handoff between centers is performed at the

midpoint of each connecting path. Flight duration is just the distance

divided by the speed except that flights within a single center area

are given arbitrarily a duration of one hour.

In Phase II of the project, when the airport-to-airport model was

introduced, it became apparent that the two models give rather

different results. Figure 1, on page 12, shows by the dotted line the

41
distribution of durations of flights between different centers under

the center-to-center model. This roughly parallels the curve for the

airport-to-airport model, but there are fewer very short flights, and

the overall average duration is 31 minutes longer. Average duration for

the airport-to-airport model is 68 minutes, and for the center-to-center

model it is 99 minutes. When one adds to each the 30 minutes that

codes are issued before departure, the result is that about 32 percent

more inter-center flights have codes at any time.

Another notable difference between the models is that 20,776

handoffs occur in the center-to-center model and 24,261 in the airportto-airport. There appear to be two reasons for the difference. Even

though two centers have a boundary segment in common, a straight line

between a point in one and a point in the other may go through part of

a third center. In the center-to-center model hand-off would be

directly between the first two rather than via the third. The second:

reason is that the boundaries of the centers are not convex. A straight

line may cross the boundary of the same center four or more times

instead of just twice. The straight- line flights of the airport-toairport model are probably a little worse in this respect than the

actual routes of the airways, but the number of hand-offs in the airportto-airport model is probably more realistic than the number in the center*

to-center.

42
The Phase I traffic sample was analyzed to see how many flights

remained within one center area and how many of those returned to the

same airport. This analysis was not repeated in Phase II, because the

results are not dependent on the model used. Tables 12-14 give the

results from Phase I. These show that of all flights 48 percent stay

within one center and 8.9 percent return to the same airport.

Other results from the center-to-center model are not tabulated

here, because the corresponding results from the airport-to-airport

model are considered more realistic.

43
Table 12. Analysis of k»cal flights

Flights with origin and destination in the same center

General Air

Center Aviation Carrier Military Total

Albuquerque 13 86 224 323

Atlanta 232 389 92 713

Great Falls 16 54 94 164

Boston 321 267 84 672

Cleveland 456 516 34 1006

Fort Worth 152 268 364 784

Washington 169 361 240 770

Denver 68 222 8 298

Houston 299 339 385 1023

Indianapolis 235 317 99 651

Jacksonville 75 122 182 379

New York 354 279 53 686

Los Angeles 395 397 180 972

Miami 82 219 120 421

Memphis 53 169 64 286

Minneapolis 105 210 91 406

Chicago 468 701 76 1245

Seattle 134 267 106 507

Oakland 98 232 121 451

Salt Lake Cy 39 67 7 113

Kansas City 175 236 88 499

Total 3939 5718 2712 12369

44
Table 13. Analysis of local flights

Flights with origin and destination airports the same

General Air

Center Aviation Carrier Military" Total

Albuquerque 1 3 204 208

Atlanta 22 2 54 78

Great Falls 1 1 87 89

Boston 14 8 55 77

Cleveland 13 2 30 45

Fort Worth 27 2 319 348

Washington 5 2 125 132

Denver 11 6 5 22

Houston 25 6 296 327

Indianapolis 3 83 86

Jacksonville 11 4 109 124

New York 8 7 16 31

Los Angeles 4 19 59 82

Miami 2 4 92 98

Memphis 5 5 39 49

Minneapolis 13 1 85 99

Chicago 31 9 50 90

Seattle 22 80 102

Oakland 4 3 102 109

Salt Lake Cy 9 7 16

Kansas City 7 3 58 68

Total 238 87 1955 2280

45
Table 14. Analysis of local flights (concluded)

Flights within one center with different Origin and destination airports

General Air

Center Aviation Carrier Military Total

Albuquerque 12 83 20 115

Atlanta 210 387 38 635

Great Falls 15 53 7 75

Boston 307 259 29 595

Cleveland 443 514 4 961

Fort Worth 125 266 45 436

Washington 164 359 115 638

Denver 57 216 3 276

Houston 274 333 89 696

Indianapolis 232 317 16 565

Jacksonville 64 118 73 255

New York 346 272 37 655

Los Angeles 391 378 121 890

Miami 80 215 28 323

Memphis 48 164 25 237

Minneapolis 92 209 6 307

Chicago 437 692 26 1155

Seattle 112 267 26 405

Oakland 94 229 19 342

Salt Lake City 30 67 97

Kansas City 168 233 30 431

Total 3701 5631 757 10089

Flights with origin and destination in different centers

Total 3860 7812 1605 13277

Total Flights 7799 13530 4317 25646

46
Appendix B

On Simulation Strategies and

Simulation Programming Languages

When this project was undertaken, one view that was expressed held

that in the long run there would be a great economy in building a very

detailed computer model of the air traffic system that would contain

every feature pertinent to almost any simulation one might wish to

undertake. The economy was expected in the ease of adapting this model

to deal with one or another question one might seek to answer by

simulation. Specifically in this project it should be very easy to

adapt this model to any code assignment plan that could be devised.

The contrary view was that no computer memory is large enough to

store all that detail and no computer fast enough to run such a simulation at a reasonable speed. ~The imperatives of economy of memory and of

computer time require that one write a specific simulation program for

each question, and that one include in it no detail not relevant to that

question. A simulation should use as simplified and abstract a model

of reality as the question posed will allow.

The second view prevailed in the execution of this project, and

the writers feel that the results amply justify this decision. Computing

time never became a limitation, but staying within memory capacity

definitely required shoehorning. The machine used is a UNIVAC 1108

with 65,536 words of memory, but only about 53,000 words are available.

to the user. Consider that 2,618 flights are in progress at one time.

For each flight one must store at least these data: (1) origin,

(2) destination, (3) speed, (4) distance travelled up to this time, and

(5) beacon code. These five items were packed into four computer words,

47
but one must also store an event notice that will call the proper

subroutine for the next event in the flight, either a handoff or an

arrival. A handoff notice contains an identifier of the flight,

identifiers of the two centers involved in the handoff, and two words

of scheduling information packed into four words in all. If there

are eight words stored for each of 2,618 flights, then 20,944 words are

used to give this minimal description of the situation. One would like to

store a few other things such as the direction cosines of the flight path

but the necessity of shoehorning dictated that they be recomputed at

each event.

Next are some data tables. For each of 1113 airports one stores

x coordinate, y coordinate, and center using 3339 words. For 587 boundary

points of centers one stores x, y, and adjacent center, using 1721 words.

Four words of results tabulated for each of 21 centers and 24 hours comes

to 2016 words. The table to show which codes are in use in which

centers might be 700 words. Finally, the SIMSCRIPT system routines, the

event routines, and necessary library routines for a typical simulation

used 12,341 words. The total of the above is 41,061 words, so there

is not much room for additional details.

Unfortunately all this has to be in memory all the time. /There is

no part that is unused long enough to permit moving it out and back in

again. If some assignment plan should exceed memory capacity in spite

of shoehorning, the most feasible tactic seems to be to simulate only

a 50 percent sample of the traffic by using every other flight and

counting two codes in use for it.

48
The running time of these simulations was gratifyingly short.

Simulating a peak day required only about 10 minutes of computer time.

For each of 27,692 flights one record was read from the exogenous

events tape y and, on the average, three event routines were performed,

a departure, a hand-off, and an arrival. This averages about 22

milliseconds per flight or only 7 milliseconds per event routine.

Those who urged the very detailed approach to simulation suggested

that each aircraft in turn be advanced by one minute's flying time then

a search be made to see whether it had crossed a center's boundary. This

would have been much slower, possibly 30 times slower. A 10 minute

simulation run is fine, but five hours?

The center assignment plan and the master assignment plan work,

so differently that they require almost completely different programs.

The center plan jumps from flight to flight always doing next whatever

departure, or handoff^ or arrival occurs next in simulated time. In

the master plan, however, the master center cannot issue a beacon code

for a new flight plan until it has simulated the whole flight to find

in which centers it will fly. So the sequence of work in the computer

is quite different for the two plans.

What the programmer must rewrite, however, is only about 350

(FORTRAN- like) SIMSCRIPT statements. Most of the 12,000 or so words

of simulation program in the computer memory are SIMSCRIPT system

routines that the programmer never has to write and which are the

same for any digital simulation whether of air traffic or anything else.

The system dynamically allocates temporary storage for descriptions of

flights and for event notices. It stacks event notices in their sequence

49
of performance and controls the progress of simulated time. It

interprets, through indirect addressing, subscripted names such as

CTRA(ORIGN(FLT)), which is the center in which is the airport that is

the origin of a particular flight. The STMSCRIPT programming language

contains the invariant structure that is useful in one simulation after

another. Thus it provides the economy that was sought in an elaborate

invariant model.

The most notable alternative to SIMSCRIPT is GPSS, which possibly

is even more popular. GPSS is based on block diagrams and requires

little experience in programming; whereas SIMSCRIPT is nearlyan extension

of FORTRAN and requires the FORTRAN level of programming skill. A

SIMSCRIPT program is easily changed by just replacing statements,

but changing a GPSS program is likely to require extensive renumbering

of blocks. Perhaps the fatal defect of GPSS for our purpose is that

it would require flights to be generated internally according to

some probability scheme such as the Poisson law. It cannot accept an external source of flights like the peak day tape. A lesser consideration

is that, while there is a very good version of GPSS for the IBM System

360, the implementation on the UNIVAC 1108 is rather primitive,

SIMSCRIPT on the 1108 proved very convenient and reliable, and the

programs should be transferable to an IBM System 360 with little change

except for control cards.

50
Appendix C

Traffic Flow Data

The following tables describe the traffic sample employed in

these simulations by giving for each center area and each hour of the

day the number of departures to each center area, the number of arrivals

from each center area, and the number of handoffs from each adjacent

center. The events called departures in these tables are really the

filing of a flight plan and the issuing of a beacon code. Actual

departure occurs one half hour later.

51
Table 15. Departures from, arrivals at, and

handoffs to each center by hours

Boston

New York

Washington

Jacksonville

Miami

Cleveland

Atlanta

Indianapolis

Chicago

Memphis

Houston

Minneapolis

Kansas City

Fort Worth

Great Falls

Denver

Albuquerque

Salt Lake City

Seattle

Oakland

Los Angeles

PAGE

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

52
NUMBER OF DEPARTURE5

; FROM BOTTOM

AT t,,vlT 1 2 3- 4 5 6 EST 20 21 22 23 24 1 TO BOSTON 28 27 34 12 8 4 NEW YOriK ii 19 12 7 3 4 WASHINGTON 2 1 1 1 t JACKSONVILLE o n n MIAMI l CLEVELAND 2 4 4 4 3 ATLANTA U 1 INDIANAPOLIS n n 2 CHICA&u n 1 1 2 1 MEMPHIS n a MINNEAPOLIS i o KANSAS CITY n n DENVER n SLATTLc D OAKLAND n o n n LOS AiJoELES u

12

7 1510

11 39 35 40 57 48 52

3 2? 35 38 24 30 32

17

12

55

17

3

18

1

1

1

18 19 20

13 14 15

55

35

2? 23

17 18

804

492

87

13 119

61647

3

36

?

16

10 96 52 52 27 1H 77 95 107 101 98 102 87 115 115 116 96 97 96 71

NUMBER OF ARRIVALS AT BOSTON

AT 6mT 1 2 . 3 4 5 6 7 8 9 10 n 12 13 14 15 16 17 16 19 20 21 22 23 24 EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

FROi-i TOTAI BOSTON 42 27 32 26 15 7 3 3 4 1 11 35 37 37 55 58 49 57 60 61 50 46 45 44 805

NEw YORK 16 17 18 8 7 6 R 2 1 1 2 10 15 17 21 20 16 24 14 29 16 26 11 23 328 WASHINGTON 9 3 3 3 1 2 5 6 5 9 6 6 5 4 8 5 8 6 94 JACKSONVILLE 1 U n n n 1 1 1 2 6 MIAMI 1 5 1 3 1 n n n 1 1 3 1 1 ? 20 CLEVELAND 8 4 6 3 1 1 l l 3 9 6 8 6 5 7 8 10 6 6 4 11 114 ATLANTA 1 (j n n 1 1 3 INDIANAPOLIS 1 n n n n 1 2 1 1 1 1 1 3 1 13 CHICAGO u 3 2 l 2 2 2 n 1 4 2 4 1 1 1 2 28 MEMPHIS n n n 1 n 1. HOUSTOn 1 l n n n n n n n ? MINNEAPOLIS n 1 n n n 1 KANSAS CITY l 1 n 1 1 1 5 FORT WORTH 1 n 1 2 DENVER n n n n .0 1 n 1 ALBUQUERQUE 1 n n n n n 1 SEATTLE 1 n n n n n n 1 OAKLANu u 1 n n 1 1 3 LOS ANto-ELES 2 a n n 1 n l 2 6

81 63 fa3 42 25 19 12 15 52 68 68 95 96 77 96 94 109 88 88 73 92 1434

NUMBER OF HANDOFFS TO BOSTON

NEW YORK CANADA CLEVELAND

AT GMT 1 2 3 4 5 6 7 8 EST 20 21 22 23 24 1 2 3

31 33 28 12 12 12 7 5

5 6 2 2 1 1

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 TOTA

3 6 23 24 40 38 32 34 30 35 40 40 32 27 50 595

•n 1 2 2 2 7

1 5 3 5 3 3 1 4 7 8 6 3 8 1 76

36 39 30 14 13 13 28 27 46 43 35 37 34 42 48 46 35 35 53
NUMBER OF DEPARTURES FROM NEW YORK

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

To EST 20 21 22 23 24 1 2 3 4 s 6 7 8 9 10 11 12 13 14 15 16 17 18 19 TOTAl BOSTON 18 2<J 7 8 9 5 2 1 1 2 10 20 19 14 22 17 19 15 25 27 20 11 22 14 328 NEW YOaK 21 25 13 13 9 6 2 CI 9 38 47 43 69 55 55 49 38 39 40 41 26 30 26 694 WASHINGTON 3 9 7 2 1 1 n 1 1 16 26 21 15 19 14 12 14 21 14 19 15 10 11 252 JACKSONVILLE 1 1 r> n n 1 2 2 1 3 2 2 1 1 2 1 3 n 23 MIAMI "* 3 1 2 a CI n 2 7 3 4 3 3 1 3 1 6 5 48 CLEVELAND 21 lfa 10 5 1 3 2 l l l 18 23 22 23 22 21 17 15 22 16 24 31 16 22 353 ATLANTa 1 1 3 2 l 2 7 4 2 1 2 4 3 2 6 5 3 49 INDIANAPOLIS 2 2 1 n n n 3 6 3 3 4 3 4 8 3 3 6 3 54 CHICAGO 7 2 6 2 8 3 2 l n 2 7 5 5 10 8 9 6 8 7 8 7 9 8 130 MEMPHIS 2 U n n n n CI n n 1 n 2 CI n n n O 2 7 HOUSTO.. a 2 2 l CI l l 3 l 1 2 2 l 1 3 1 2? MINNEAPOLIS n n l n a 1 n CI 1 n n 2 1 1 1 8 KANSAS CITY u l l n CI n 2 4 1 1 2 a 2 2 4 ? 2? FORT WORTH u (J n n n n n CI 1 3 1 n 2 2 1 10 DENVER n n CI n 2 n n 1 n l n 3 n 7 ALBUQUi-R&UE n n n n n n n 1 n n n CI n n n 1 n 2 SALT LAKE CY C! u 1 n n n n CI n n n n n n l 2 SEATTLl. n n n CI n CI l n n n CI n n n 1 n 2 OAKLANU 1 2 1 3 n n 2 2 4 l l 2 3 l l l 2 2 29 LOS ANGELES u 1 l 1 1 CI 2 3 3 n l 1 1 1 2 1 3 2?

60 81 46 40 30 19 16 14 88 137 135 153 147 127 126 101 130 123 124 119 119 99 2064

NUMBER OF ARRIVALS AT NEW YORK

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 FROM TOTA BOSTON 17 24 18 13 b 3 4 2 2 1 5 25 32 30 31 29 33 15 35 28 37 30 36 35 491 NEW YOivK 30 19 20 17 11 9 5 2 16 38 42 46 64 65 51 46 42 36 46 39 26 25 695 WASHINGTON 18 2b 21 B 4 1 2 5 2 3 12 22 23 32 29 27 26 20 27 34 25. 19 32 417 JACKSONVILLE 3 3 CI 1 1 2 2 1 1 3 2 1 n 1 1 4 5 31 MIAMI 4 9 1 1 12 1 1 n

' 1 n 2 7 7 1 2 12 9 9 7 5 91 CLEVELAND 15 17 20 5 2 8 4 2 1 5 8 30 25 28 20 28 17 24 23 28 32 24 24 393 ATLANTA 7 6 3 2 5 2 3 CI 3 1 1 4 1 3 6 6 3 1 6 7 7 79 INDIANAPOLIS 4 3 1 3 1 2 1 n 2 3 8 2 2 3 3 4 5 5 8 60 CHICAGO 8 6 7 6 6 8 3 1 2 l 4 3 6 8 5 3 10 4 7 10 9 6 124 MEMPHIS 1 CI n 1 1 1 1 1 1 7 HOUSTON 1 2 1 2 1 CI CI 2 2 3 1 1 I 1 19 MINNEAPOLIS 1 2 1 1 n n 1 1 3 2 2 14 KANSAS CITY 3 6 2 1 2 1 l l 4 1 1 2 2 4 1 3 36 FORT WORTH 4 1 1 1 l n n 1 4 1 3 1 1 2 21 DENVER 1 n l n n n 3 2 n 7 ALBUQUtK&UE 1 l n n 2 n n 5 SEATTLE II n Cl 2 n n n n n 3 n n n 2 7 OAKLANu 2 1 2 2 1 4 2 1 CI 1 l 6 5 3 2 3 36 LOS ANGELES 3 1 1 1 3 CI 6 3 1 l CI 1 7 3 2 5 38

120 126 98 55 39 47 28 11 20 19 43 89 136 134 170 173 164 123 150 157 189 170 148 162 2571

NUMBER OF HANDOFFS TO NEW YORK

AT &MT EST221

322

4 5 23 24

10

5 1510 17

12" 23

18

BOSTON WASHINGTON CLEVELAND3046

51

14

1329

7

1016

54

35

57

47

49

55

4443

60

53

63

79

57 43

58 54 53 68

764

820 1012

126 127 85 52 56 37 18 18 29 15 33 104 146 158 143 150 151 116 147 182 195 175 168 165 2596
NUMBER OF DEPARTURES FROM WASHINGTON

TO BOSTON

NEK YO,<K WASHINGTON

JACKSONVILLE

MIAMI

Ci-EVELhND ATLANTA INDIANAPOLIS

CHICAGO

MEMPHIS

HOUSTO,. MINNEAPOLIS

KANSAS CITY FOKT WuRTH GREAT FALLS DENVER ALBUQUlRGUE

SEATTLtu OAKLANu

LOS ANuELES

TOTAu

AT omT 1 2 3 4 5 6 7 EST 20 21 22 23 24 1 2

2 3 2 22 20 13 3 3 31 23 26 5 7 3 2

3 2 1

[) 1 (1 3 2 6 7 3 1 2 1 1 4 1 2 1 4 2 2

1 1 2

1 n

u 1

1 1 u u n n

u

u n n

1 n n

1 n

o

nn

n

12

7

25

41

4

313

11

6

8 3069

66

S16

4

6

2

1?

15

10

fl 26

54

6

24

54

4

2

512

7

7

2

2

2

1

25

51

9

3

7

B2

4

2

2

3

19

14

7 26

64

B

1

3"S 61

fl3

fl7

3

113

n

loo

o

o

o

2044

7

6

7

8

3

3

1

2

1

26

2fl2

16

10

94 417

fllO 84

3? 10?

141

an5437

16

7

2119

14

1

15

12 78 5b 56 14 11 19 49 124 158 145 145 123 129 122 146 136 110 103 97 93 1938

NUMBER OF ARRIVALS AT WASHINGTON

AT G'vlT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 2? 23 24 EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

FRO.'i TOTA

BOSTON 3 3 1 2 1 n () n 3 6 7 9 7 2 3 5 2 10 9 a 5 87 NEW YOkK 11 3 10 6 1 2 n 1 l 11 24 2fl 13 23 13 8 17 19 16 15 17 12 252 WASHINGTON 31 36 27 22 7 5 4 1 16 26 45 56 71 77 51 SI 51 67 50 56 27 31 810 JACKSONVILLE 8 3 6 2 2 2 n 1 1 2 8 1 4 8 6 5 5 5 4 6 an MIAMI 2 2 n 2 n n 1 5 1 1 3 2 6 ? ? 29 CLEVELAND 8 a 3 1 n 11 9 4 7 13 6 8 11 10 7 3 3 113 ATLANTm 9 4 6 4 4 3 l l 1 5 5 8 11 14 5 17 7 5 9 13 13 145 INDIANhPOLIS 8 4 7 4 l 5 7 6 8 7 12 5 11 3 5 9 105 CHICAGO 1 5 3 4 2 3 1 n 1 3 4 2 1 3 3 3 1 2 45 MEMPHIS 2 3 1 1 2 n 1 1 1 3 3 1 23 HOUSTON 1 ? 1 n n 1 1 3 1 1 n 1? MINNEAPOLIS i n n n n n n n n l 2 KANSAS CITY 1 2 1 n n n n n n 1 1 1 2 1 n 3 2 16 FORT WORTH 3 1 2 1 l n n 1 1 1 2 1 I 20 DENVER 1 1 1 n n n n n n 2 n "n 5 ALBUQUC.RQUE 1 r n n n n n n n n n 1 SEATTLE u n n n n n n l 2 n 4 OAKLANu 2 n l n n 1 n 5 LOS ANGELES ? 1 1 n 3 1 n n 1 n 3 l n l 14 TOTAL 95 71 68 49 22 18 12 fl 3 4 22 42 93 li? 1?5 143 114 92 130 128 124 118 a7 88 1768

NUMBER OF HANDOFFS TO WASHINGTON

FRO.'i NEW YOkK JACKSONVILLE

CLEVELAND

ATLANTA INDIANAPOLIS

TOTAL

AT GMT 1 2 3 4 5 6 7 fl 9 EST 20 21 22 23 24 1 2 3 4

22 11 21 7 12 4 4 3 22 5 5 3 20 3 1 2 3 29 12 12 8 7 5 3 2 3 25 17 8 fl 11 4 2 3 2 12 5 7 3 3 3 1 4

1 12 13 14 15 16 17 18 19 20 21 22 23 24

6 7 8 9 10 11 12 13 14 15 16 17 18 19

26 47 52 37 44 23 28 41 30 36 29 44 35

110 50 53 29 53 19 11 14

2 1 3 4 14 21 11 11 19 21 18 19 18 24 25?

3 2 13 17 8 18 17 11 22 23 27 17 13 17 290

2 3 R 14 17 22 26 19 19 19 19 31 24 15 32?

1 2 7 4 11 13 5 9 13 13 7 6 10 139

1 32 73 94 RO 116 90 74 110 106 113 103 105 101 1563
NUMBER OF DEPARTURE? FROM JACKSONVILLE

AT GMT EST

TO BOSTON

NEW YOKK WASHINGTON JACKSONVILLE

MIAMI CLEVELAND

ATLANTA INDIANAPOLIS CHICAGu

MEMPHIS

HOUSTO,. MINNEAPOLIS

KANSAS CITY FORT WORTH ALBUQUERQUE

OAKLANJ

LOS ANoELES

TOTAu

1 2 3 4 5 6 7 8 9 10 11 12 13 m 15 16 17 18 19 20 21 22 23 24

20 21 22 23 24 l 2 3 14 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

TOTA1

u n n n n n 1 n 1 1 1 1 1 6

1 l n 3 l n 1 2 3 2 1 2 4 4 4 2 31 4 3 1 n 2 1 2 l 1 2 8 2 14 8 7 6 4 4 5 9 6 80 23 14 12 9 4 "4 l 5 3 3 16 22 56 36 <42 46 35 44 44 33 26 34 21 533

7 7 3 3 14 2 1 2 2 14 7 2 6 7 6 4 13 6 8 8 11 11 124

1 1 1 l n n n n 1 1 1 1 3 ? 1 15

7 5 5 9 2 2 l l 14 2 12 16 20 16 14 16 11 12 19 15 23 14 16 24?

n n n n 1 1 1 3 3 2 1 1?

1 n n n n 2 n 1 1 1 1 1 8

1 n n n n 1 2 l 1 1 1 3 2 1 1 16

1 1 1 l 1 n n 1 2 3 14 1 6 1 5 2 2 5 2 4n

n n n n n 1 n n n n n 1 1 a n n n n n n 2 l n 2 n 6

n n n 1 3 1 2 l 1 4 l 1 16

1 n n n n n 1 n n 2 l 1 o' 6

1 n n n n n n 2 4 2 2 U 3 n n n 3 1 1 4 n 2 2? 49 33 27 27 12 35 54 99 71 79 87 67 93 85 76 81 78 65 116?

NUMBER OF ARRIVALS AT JACKSONVILLE

FRO.-, BOSTON

NEW YORK WASHINGTON JACKSONVILLE

MIAMI CLEVELAND

ATLANTA INDIANAPOLIS CHICAGO

MLMPHIb

HOUSTON MINNEAPOLIS

KANSAS CITY

FORT WORTH ALBUQUERQUE

SEATTLE OAKLAND

LOS ANjELES

TOTAL

AT G^T 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 TOTA

n n n n (1 n 1 n 1 1 1 4

2 1 l u 1 n 3 2 1 3 3 2 1 2 1 23

6 5 l 2 1 1 2 4 1 5 4 8 7 5 11 7 6 8 84

29 21 17 13 7 5 3 1 4 5 5 13 16 41 50 39 50 32 40 41 42 35 24 533

3 4 7 5 3 2 1 1 1 1 1 1 5 8 6 6 6 8 7 15 12 9 6 118

1 n 1 n n n 1 1 1 2 1 0' 8 11 7 11 8 7 5 1 l 1 5 7 8 5 16 18 12 11 14 18 17 U 194

1 1 n 1 2 2 ? 1 ? 3 2 17

2 1 n n n n n 1 n 1 1 6

2 U 1 1 n n 1 2 l 5 1 3 1 18

3 2 3 6 1 l 3 3 7 7 4 2 5 6 1 54

n n 1 1 1 1 n n l 2 1 1 n 7

1 3 1 1 l 2 3 2 1 2 1 1 1 20

1 1 n n 1 1 1 5

a n n n n 1 1 1 1 n n l n n 1 n 4

2 1 l n 1 l n n 1 1 1 2 11

60 49 44 37 22 14 5 3 2 6 8 9 24 34 6"7 71 83 "94 70 88 91 92 84 51 1108

NUMBER OF HANDOFFS TO JACKSONVILLE

AT GMT' 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 FROM TOTA WASHINGTON 13 5 8 2 2 4 1 1 5 5. 9 23 16 15 11 18 17 14 8 11 9 197 MIAMI 22 10 10 27 17 6 3 3 2 2 n 2 6 28 37 20 20 18 46 51 40 43 37 34 484 ATLANTA 31 33 23 25 15 19 4 4 2 1 2 4 11 19 21 22 44 53 30 4? 38 48 37 32 560 HOUSTON 9 6 8 8 2 1 1 ? 4 6 9 10 8 13 8 10 6 6 117

75 54 49 62 36 25 11 3 11 22 58 85 64 88 92 102 123 100 109 91 81 1358
NUMBER OF DEPARTURES FROM MIAMI

AT GMT 1 2 3 4 ' 5 6 7 8 9 in 11 12 13 it 15 16 17 18 19 20 21 22 23 24

TO EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 ID 11 12 13 14 15 16 17 18 19

TOTAI BOSTON 1 2 2 n n n n 1 1 4 1 2 1 4 1 20 NEW YOKK 11 2 1 1 n n l 5 7 4 3 5 12 9 6 8 4 a 4 91 WASHINGTON u 2 n n l 6 l 2 1 3 n 6 1 1 4 1 29 JACKSONVILLE 3 b 5 4 1 l n 1 n 1 3 9 10 8 4 3 11 6 11 14 10 2 5 118 MIAMI 11 la 13 10 9 3 6 5 2 l 16 30 43 28 ?3 29 20 28 36 26 22 23 14 15 431 CLEVELhND 1 l 2 3 1 1 n n 1 3 2 2 1 4 5 2 4 ? 3 3 41 ATLANTA 2 1 2 1 2 2 1 1 l n 2 9 1 4 4 1 6 10 1 8 10 2 4 75

INUIANrtPOLIS u 2 l n n 1 n 3 2 n 2 n 3 14 CHICAGO u 6 1 n n n l 3 1 2 7 2 3 3 3 32 MEMPHIS n n n n 1 1 n 1 2 n 1 ft HOUSTON 1 n n n 1 7 n 1 1 5 2 3 l 3 1 2ft KANSAS CITY n n n n n n l n n 1 n n 4 n n 1 7 FORT WoRTH 1 n n n n n 2 4 l n l l n 10 ALBUQUERQUE n n n n n n n 1 n n n n 1 OAKLANo n n n n n n n 1 n n n n n 1 LOS ANoELES n n n n n n l n 1 n n n n l n n 3 19 27 41 27 14 18 36 71 68 u3 48 35 76 84 56 72 57 45 41

MUMBER OF ARRIVALS AT MIAMI

FRO.i BOSTON

NEW YOKK WASHINGTON JACKSONVILLE

MIAMI CLEVELAND

ATLANTA INDIANAPOLIS

CHICAGO

MEMPHIS HOUSTON

KANSAS CITY FORT WORTH DENVER ALBUQUERQUE

OAKLAND

LOS ANoELES

TOTAu

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 2? 23 24

!0 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

TOTAI

3 U 1 1 n n l 1 3 1 n 2 n n 13

4 2 1 5 1 1 2 n n n l 6 3 4 4 3 2 3 6 48

3 1 n n 6 4 3 3 3 2 3 3 l 3?

.6 10 b 8 3 3 2 2 1 2 2 5 5 5 4 7 7 8 10 5 6 7 124

.8 8 20 14 11 4 7 4 3 3 3 15 30 31 33 27 26 30 31 26 26 2? 24 15 431

1 1 1 1 2 n 3 3 2 2 3 1 n 20

3 13 5 3 3 2 1 n 1 2 l 2 2 2 7 7 8 4 9 8 5 98

2 2 2 2 1 n 1 n n 1 3 2 3 2 1 1 2 25

2 1 1 1 2 9 n n n n 2 4 3 2 3 3 1 34

1 n n 1 n l 1 1 2 n 7

6 3 2 2 1 1 n n n 4 1 1 1 2 3 27

1 1 1 n l n n n 1 1 1 2 n 1 in

1 n n n n n n l n 1 l n n 4

1 n n n n n n n n n n n n i 1 n n n n n 1 n 1 l n 1 5

n l n n n n 1 n n 2

1 n 1 n n n n n n 1 n n 3 34 49 38 21 21 19 34 37 54 55 49 65 61 56 56 46 46 37

NUMBER OF HANDOFFS TO MIAMI

FROi.i JACKSONVILLE

TOTAL

AT GMT 12 3 4 EST 20 21 22 23

36 25 31 18 12 18 36 25 31 18 12 185 5 3

5 5 3

11 12 13 14 15 16

5 6 7 8 9 10 11

3 4 8

8" 20 34

3 4 8 8 20 34

17 18 19 20 21 22 23 24

12 13 14 15 16 17 18 19 TOTAL

32 28 33 34 26 28 20 32 463

32 28 33 34 26 28 20 32 463
NUMBER OF DEPARTURES FROM CLEVELAND

AT GMT 1 2 3 4 5 6 7 8 9 in n 12 13 14 15 16 17 18 19 20 21 22 23 24 EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 TO TOTAl BOSTON 5 4 2 1 1 2 2 6 6 9 5 5 8 4 8 9 7 5 7 11 7 114

Ntrt YOKK 19 19 It 3 8 3 4 1 5 4 11 29 26 30 22 21 21 24 24 29 3n 2? 26 a 393 WASHINGTON 5 3 1 (J 1 n n 3 12 6 6 7 14 6 7 in in 6 2 4 10 113 JACKSONVILLE 1 fl n n a n n a 11 1 n 1 D 1 2 l n n i a MIAMI 1 2 1 1 a n n 5 4 1 3 1 n n l 20 CLEVELAND 30 32 22 24 13 13 4 6 4 8 33 82 71 67 74 49 59 72 69 64 70 57 48 43 1014 ATLANTA 1 2 2 2 1 1 1 1 4 5 3 4 3 2 4 4 2 6 4 3 55 INDIANmPOLIS 8 3 2 3 4 1 3 3 2 8 22 14 25 15 14 9 21 20 It 15 6 10 4 231 CHICAGO 8 12 8 11 6 2 3 4 5 6 6 21 20 ?n 23 21 18 15 25 18 19 18 14 14 317 MEMPHIi • J 1 2 n 1 n n 2 1 1 1 2 n 1 n 1 n 13 HOUSTOi. n a n n n n n 1 n n 1 n n n 2 MINNEAPOLIS 1 i 2 n 1 n 1 6 7 6 1 6 4 4 2 4 7 2 1 56 KANSAS CITY 4 u 3 i 1 2 1 1 1 1 6 2 1 2 1 3 2 4 1 4 2 43 FOKT WORTH u n (1 n n n fl 1 1 n (1 1 2 n 1 n n 6 GREAT FALLS u 1 n n n n n n n n n n n n n n n n 1 DENVER 1 J n n n n n n 1 n n 2 OAKLANo o n n l n n n n l 3 n n n l n l 7 LOS ANoELES V l 1 l l n l l l 2 4 n l 2 2 18 83 82 45 50 37 21 15 20 20 25 70 186 167 173 164 140 131 158 174 149 153 134 123 93 2413

NUMBER OF ARRIVALS AT CLEVFLAND

FROi-i bOSTON

NtW YOKI< WASHINu

JACKSO,. MIAMI CLEVEL

AIl-ANT INDIAN CH1CAG

MLMPHI

HOUSTOi MINNEAr KANSAS

FOKT W

OAKLAND

LOS ANo

TOTAl.

TON VILLE

NDPOLIS

OLIS

CITY RTH

AT GMT 1 2 3 4 5 6 7 a 9 in 11 12 13 14 15 16 17 18 19 20 21 22 23 24 EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 TOTA

a 1 7 2 5 3 2 1 n 8 a 6 7 6 5 6 6 6 13 6 3 in 119

24 21 17 9 5 2 3 3 1 1 16 20 23 20 24 19 21 14 19 16 23 31 20 35?

8 5 2 6 n n n l 3 7 9 6 4 6 4 9 9 9 4 6 4 10?

2 U 2 1 1 1 n l n n n n n 1 1 1 1 1 2 15

1 5 1 1 2 4 l l a n n 1 1 2 3 2 2 3 5 2 4 41 43 29 33 24 21 12 12 5 5 3 8 51 73 65 67 78 55 51 66 75 65 73 64 36 1014

9 5 1 1 2 1 n 2 1 n 1 2 3 2 2 2 6 2 3 5 50

11 13 9 4 5 4 3 3 1 l 1 in 10 9 7 7 11 11 10 15 15 24 18 202

24 16 14 9 13 9 3 3 2 l n 4 6 17 16 16 8 16 16 15 23 28 23 17 299

1 1 n n n n n n 2 1 1 2 n 2 2 2 1 15

u 1 n n n n n n n n n 1 n n n n n n 2 4 1 4 2 1 i n 1 a 2 4 2 3 3 3 3 a 1 2 1 n 46

1 2 1 1 n 2 n n n n n 1 1 3 2 3 1 2 n 2n

u n n n n n n n n n n n n n n 2 n n ?

2 u n 1 n n n n n n n n n l n 1 n n 1 6

1 2 l 1 l n 3

" l n l n n n n n 5 n n 1 17

139 99 89 63 55 38 24 21 12 6 16 84 126 137 129 144 ill 122 133 152 159 165 161 117 2302

NUMBER OF HAMDOFFS TO CLEVELAND

AT GmT 1 2 3 4 5 6 7 a 9 in 11 12 13 14 15 16 17 18 19 2n 21 22 23 24 EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

FRO,'! TOTA BOSTON 2 3 5 1 4 1 1 1 5 7 7 5 4 5 11 2 6 7 3 4 a 9? NEW YOUK 53 49 22 23 18 16 10 in 4 4 3 32 63 63 60 51 66 37 40 60 64 66 68 53 935 WASHINGTON 17 1U 9 6 10 1 l n 2 7 19 15 15 18 23 19 9 25 16 14 21 16 273 CANADA 10 7 5 1 1 2 l 3 n 5 4 9 7 11 12 12 13 9 10 3 12 17 154 INDIANAPOLIS 53 29 25 18 10 13 9 8 4 6 14 4 24 22 20 28 18 34 43 41 48 51 47 45 614 CHICAGO 46 29 25 20 31 12 4 15 7 4 5 11 2n 38 24 24 23 38 42 49 50 52 38 39 646 MINNEAPOLIS 4 1 3 1 1 2 n 1 2 1 3 1 4 2 2 5 1 1 3 1 39 TOTAL 185 128 91 72 75 45 24 36 20 14 26 66 138 157 132 140 149 153 154 191 195 190 193 179 2753
NUMBER OF DEPARTURES FROM ATLANTA

AT GMT 1 2 3 It 5 6 7 8 9 in 11 12 13 14 15 16 17 18 19 20 21 22 23 24 EST 20 21 22 23 24 1 2 3 it 5 6 7 fl 9 10 11 12 13 14 15 16 17 18 19

TO TOTAl BOSTON t) i) il n n l fl n n n n n n n 1 1 3 NEW YOrvK 4 3 2 2 2 1 2 l 2 1 2 2 5 l l 4 fl 2 4 6 5 7 5 7 79 W-ASHINuTON 7 3 2 5 2 1 1 1 4 R 11 12 9 8 16 6 7 14 11 8 9 145 JACKSONVILLE 5 12 8 7 4 1 l 8 9 4 8 16 16 13 14 13 19 15 10 11 194 MIAMI 7 10 4 1 2 1 1 n 1 4 n 4 1 5 11 7 4 7 9 5 7 7 98

CLEVELnlJD 3 2 1 1 1 l 1 1 l 1 1 2 3 4 5 3 3 6 7 3 50 ATLANTA JO 37 18 Id 6 6 3 3 2 3 5 21 43 39 40 45 48 55 58 48 43 60 43 38 710 INDIANaPOLIS 8 3 1 2 l* n 3 4 6 2 fl 7 8 8 7 fl 5 6 5 9fi CHICAGu 4 1 1 1 1 2 I 2 1 4 3 3 2 2 2 4 1 35

MEMPHIS. b 7 5 u 2 1 2 l 3 It 11 10 16 16 13 7 6 15 6 9 4 153 HOUSTON 4 3 2 2 1 1 n 1 3 2 2 4 4 2 8 7 2 6 5 fl 4 1 7? MINNEAPOLIS U (1 n n n n n 1 1 n n n ? KANSAS CITY 1 n n l n n n 1 1 1 2 1 l 9 FOKT WORTH 1 1 1 1 n l 1 2 1 2 1 1 2 2 2 2 4 2 3 30 DENVER 1 11 n n n o n n n n n 2 n n n n 3 ALBUQUERQUE u o n o n n n 2 n n 1 n 1 n 4 OAKLANu 1 1 i n n n n n n n n 1 n 4 LOS ANoELES 1 o o n n n n n l n n n n 2

76 87 43 3S 22 13 12 12 15 52 89 82 83 114 131 130 114 109 128 129 108 91 1688

NUMBER OF ARRIVALS /IT ATLANTA

AT GMT 1 2 3 4 5 6 7 a 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 FRO- TOTAl BOSTON 1 n n 2 n 1 1 1 6 NEW YORK 2 5 1 1 1 3 1 2 n 1 3 5 3 3 4 2 1 2 3 1 5 49 WASHINGTON 9 8 2 5 2 1 l 1 2 7 14 12 7 5 1 1 fl 10 fl fl 9 11 14.1 JACKSONVILLE 17 9 6 7 3 6 2 l 1 4 3 10 15 23 17 12 14 10 15 13 21 19 14 242 MIAMI 8 3 1 3 1 1 2 l 1 2 1 6 3 2 4 3 2 fl 5 R 9 1 75 CLEVELAND 5 2 2 2 2 1 2 1 1 7 3 5 3 3 5 2 2 4 3 55 ATLANTA 37 31 36 21 14 6 7 2 3 2 2 11 lfl 37 48 46 39 45 53 55 49 4fl 56 44 710 INDIANAPOLIS 10 6 2 2 4 1 1 3 1 fl fl 6 7 8 6 2 14 10 11 4 114 CHICAGO 1 3 1 2 1 2 1 1 3 1 4 2 2 3 2 4 33 MEMPHIS 5 3 3 5 1 2 1 1 3 5 7 9 5 8 fl 9 fl 10 7 10 no

HOUSTON 4 5 1 2 2 1 1 1 3 3 2 4 2 3 4 4 2 4 3 51 MINNEAPOLIS n n 1 n 1 n 2 KANSAS CITY 1 1 n 1 2 1 1 2 2 3 14 FORT WORTH 1 2 1 1 1 3 l 2 2 4 2 6 2 3 2 3 36 DENVER 1 n n n 1 ALBUQUlRQUE 1 n n n n n 1 n 2 SALT LaKE cy II 1 n n n n n n 1 OAKLANJ 1 1 n n n n 1 1 4 LOS ANoELES u 1 1 n n n 1 n 1 1 5

101 79 57 48 33 22 17 10 12 13 19 44 107 113 99 R3 104 101 116 112 122 126 107 1651

NUMBER OF HANDOFFS TO ATLANTA

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 EST 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

FRO,«i TOTA WASHlNoTON 19 12 3 11 8 3 1 4 n 1 7 21 29 17 18 21 20 11 24 15 14 20 17 296 JACKSONVILLE 39 21 7 28 19 6 6 6 3 l 5 6 13 28 52 27 24 34 30 56 34 58 45 39 587 INDIANAPOLIS 23 8 10 7 13 8 3 1 2 3 8 21 23 18 19 21 21 23 25 22 17 24 320 MEMPHIS 26 11 12 11 9 6 6 2 4 5 1 3 10 14 16 21 23 27 25 26 25 31 19 28 361 HOUSTON 3 3 1 3 1 1 1 2 4 3 2 3 1 4 3 3 5 1 1 45 TOTAL 110 55 33 60 50 23 15 11 12 8 10 )6 54 96 111 86 90 103 91 132 102 130 102 109 1609
NUMBER OF DEPARTURES FROM INDIANAPOLIS

AT GMT 1 2 3 4 5 6 7 fl 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

TO CST 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 lfl TOTA BOSTON n 1 1 1 n 1 1 1 1 ? 3 1 13 NEK YORK 1 1 3 1 1 1 3 4 3 5 3 5 2 3 8 5 7 4 60 WASHINoTON 1 5 6 3 3 1 2 7 7 4 10 9 7 9 7 4 fl fl 4 105 JACKSONVILLE u 1 n n n 2 1 1 1 3 3 2 1 2 17 MIAMI J 2 l 1 n n 1 1 5 1 3 1 2 3 1 1 2 25 CLEVELAND It 6 7 4 3 4 1 l 2 1 2 8 10 6 10 7 12 10 10 18 20 22 13 11 202 ATLANTA 1* 2 4 1 1 1 1 2 1 6 5 10 6 7 4 7 7 12 10 9 6 8 114 INDIANAPOLIS 36 26 18 20 9 2 2 2 15 41 50 56 46 36 39 34 51 51 44 52 37 667 CHICAGO 10 5 7 3 4 1 1 2 2 16 15 7 6 9 5 4 fl 13 fl 12 8 146 MEMPHIS 2 3 4 1 1 1 1 9 5 4 5 6 2 3 4 3 3 4 - 61 HOUSTON 3 n n fl 1 2 1 1 n 1 9 MINNEAPOLIS 1 n n n n 1 n 1 2 1 6 KANSAS CITY 2 7 4 1 l 1 l 5 3 5 5 4 4 7 2 5 1 5 1 64 FORT WORTH 1 a n n O 1 2 2 1 1 2 2 1 2 1 16 DENVER n n n 1 n n 1 ALBUQUtRQUE 1 u n l 1 2 n 3 fl OAKLANli a n 1 n n 1 n n 2 LOS ANGELES n n n 1 n n 1 n 2 4 TOTAL 75 56 53 36 22 10 7 4 3 4 10 44 92 116 104 88 88 93 77 113 125 104 ill fl5 1520 NUMBER OF ARRIVALS AT INDIANAPOLIS

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 CST 19 21) 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

FROri TOTA BOSTON 2 1 1 n n 1 1 2 1 1 2 1 2 1 , 16 NEW YOkK 3 6 2 1 n 1 1 3 4 2 5 2 4 7 6 1 6 54 WASHINGTON 5 3 2 1 2 1 3 3 8 4 6 4 7 2 4 5 7 7 6

" 80 JACKSONVILLE U 1 n n n n 1 1 2 1 4 2 12 MIAMI 2 1 2 l n 1 2 3 2 14 CLEVELAND 8 6 6 4 2 3 2 1 3 4 7 20 12 23 16 13 14 22 17 13 12 14 8 231 ATLANTA 7 8 6 1 2 2 2 1 7 4 2 7 7 5 7 10 7 6 4 95 INDIANAPOLIS 38 3d 23 16 22 6 4 2 22 34 50 57 48 35 44 32 51 49 45 50 667 CHICASO 14 9 7 5 11 3 2 4 3 13 10 fl 10 10 fl 16 7 14 15 10 181 MEMPHIS 3 2 2 1 1 2 5 1 3 3 1 3 4 1 7 3 43 HOUSTON 11 n n 1 1 n 1 3 MINNEAPOLIS 1 1 n n n O n 2 n 1 1 6 KANSAS CITY 2 3 1 1 3 1 l 1 n 2 3 5 2 1 2 5 4 5 5 2 50 FORT WORTH 1 1 1 1 n n n 2 2 1 1 11 DENVER 1 n n n n n 1 ALBUQUERQUE 1 0. n 1 n 2 OAKLANu U l l n n n 1 n 3 LOS ANuELES u n 2 1 2 5 TOTAL H2 83 52 29 40 18 9 9 4 7 9 17 55 79 in7 97 93 n5 on Q2 1 13 106 ins 90 1474

NUMBER OF HANDOFFS TO INDIANAPOI IS

FROAT GMT CST

2 3 20 21

5 6 23 24

12

6 15.9 20 21 22 23 24

14 15 16 17 18

WASHINGTON CLEVELAND

ATLANTA CHICAGO

MEMPHIS

KANSAS CITY

TOTAL

31623

16

4 10

15

931

6

6

20

4

1252

1128

1012

737

13

30

14

6

1038

2024

1610

639

2fl 35

14

19

1232

2126

1715

146 586

290

541 198 186

119 72 62 34 67 39 24 16 16 33 20 30 84 95 125 98 107 107 118 159 141 123 123 135 1947
NUMBER OF DEPARTURES FROM CHICAGO

AT 5MT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

CST 19 20 21 22 23 24 1 2 3 H 5 6 7 a 9 10 11 12 13 14 15 16 17 18 TO TOTAl BOSTON 2 1 2 2 2 n 1

' n n 1 2 3 1 3 1 1 n 3 n 3 28

Ntw YOkK b b 9 6 5 2 3 3 3 6 6 6 5 3 9 8 9 7 6 9 9 124 WASHINGTON 1 5 1 S 1 1 n 2 4 3 1 4 1 3 2 3 2 2 4 45 JACKSONVILLE 1 n n n n (1 1 n 1 1 n 1 n n 1 6 MIAMI 1 11 n n n n n 1 3 4 3 3 2 2 3 1 34 CLEVELAND 17 11) 9 14 8 4 3 1 l 3 9 18 15 12 14 14 17 12 26 27 28 16 21 299 ATLANTA 1 2 1 1 2 l n 1 1 1 2 4 2 1 2 3 3 1 2 2 33 INDIANAPOLIS fa 7 b 11 3 1 1 2 3 6 16 9 6 8 10 12 15 9 11 15 8 17 181 CHICAGO 57 5b 16 6b 29 11 9 fi 3 2 2 23 62 91 109 89 83 74 6« 82 85 93 90 81 1318 MEMPHIb 1 J 1 n n n n 1 1 3 2 3 2 1 n 2 1 1 19 HOUSTON a 2 n n n n 1 n n 1 3 n n 1 1 3 12 MINNEAPOLIS 12 11 13 li 6 3 2 2 i 1 4 14 15 fl 13 8 a 10 9 a 4 6 169 KANSAS CITY 7 11 a 4 7 3 3 1 1 l 2 13 15 13 12 14 13 li 11 8 11 19 13 201 FORT WORTH 3 2 3 2 n 3 4 1 3 2 2 2 3 ? 3 5 1 ? 43 GREAT FALLS (1 n n n n n n n n n n 3 (1 n n n 3 DENVER 3 1 1 1 2 3 1 2 l n n 2 5 1 6 3 3 2 2 3 4 4 53 ALBUQUcRQUE 1 3 1 n n n ? n n 3 3 1 2 2 1 2 ? ? 25 SALT LAKE CY U n n n n n n n n n n 1 n 1 n 1 l n 4 SEATTLE 1 1 1 l l 1 l n n n 3 1 1 1 n 1 i 4 19 OAKLAND ? 2 1 n 2 3 n n l 4 2 3 3 2 3 ? 3(1 LOS AN&ELES 2 3 3 2 2 l 2 1 2 1 l l 4 5 2 4 4 3 3 1 5 3 55

122 123 104 135 62 28 23 25 13 12 14 51 132 168 182 166 167 152 149 171 166 185 172 179 2701

NUMBER OF ARRIVALS AT CHICAGO

AT GmT 1 2 3 4 5 6 7 a 9 10 11 12 13 14 15 16 17 18 19 20 21 2? 23 24 CST 19 20 21 22 23 24 1 2 3 4 5 6 7 a 9 10 11 12 13 14 15 16 17 18

FRO.-, TOTAL BOSTON 3 1 2 1 2 1 n 5 2 3 3 3 1 5 6 5 3 1 47 NE* YOKK fa 8 5 2 4 5 6 1 3 2 3 9 6 3 12 6 10 7~ 6 8 9 9 130 WASHINGTON 3 2 2 ? 2 n n 2 4 3 6 4 2 3 6 4 2 7 54 JACKSONVILLE 1 U 1 1 n n n 2 1 1 1 8 MIAMI 4 1 2 1 5 1 n n n 4 1 2 n 1 6 1 3 32 CLEVELAND 16 12 9 10 10 3 4 3 4 3 7 8 18 20 20 23 21 17 14 22 22 17 21 13 317 ATLANTA 4 2 1 1 3 2 1 l 1 1 1 1 2 2 3 1 3 3 2 35 INDIANAPOLIS 6 15 5 6 4 2 3 2 1 n 2 13 15 6 8 9 7 4 6 12 8 12 146 CHICAGO H6 63 53 45 67 26 10 9 6 4 3 4 21 64 98 105 92 79 71 68 84 76 98 86 1318 MEMPHIb 1 1 1 1 1 n n n 1 2 1 4 3 2 1 4 3 4 30 HOUSTON 2 2 1 2 n n n n n n 1 2 1 n 3 n 1 n 15 MINNEAPOLIS 14 1U 10 3 2 2 1 l 1 n 5 12 12 8 11 14 14 10 11 14 13 14 11 193 KANSAS CITY lb 15 7 7 5 3 2 5 l l 1 2 6 15 10 10 8 14 6 10 15 7 10 176 FORT WORTH 2 fa 1 2 1 n n 1 2 6 3 3 2 2 3 3 2 6 45 GREAT FALLS 1 1 n n n n n n n n n n n ? DENVER 5 3 2 2 4 1 1 1 1 l 3 4 2 2 1 6 4 5 3 ? 2 55

ALBUQULRtiUE 1 2 1 1 n n 2 n 1 3 l 1 1 3 1 18 SALT LAKE CY 1 n n n n n n 1 n 1 n 3 SEATTLt 2 4 l n 2 3 n n 5 2 l 4 1 l 26 OAKLANu 3 4 2 l l 1 2 2 3 1 n 1 6 2 3 2 2 2 38 LOS ANGELES 2 4 8 2 1 1 1 4 2 6 4 8 3 2 4 6 58 TOTAL 177 156 112 87 106 52 30 19 24 21 21 29 60 139 175 179 179 157 159 147 175 179 186 177 2746 NUMBER OF HANDOFFS TO CHICAGO

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

FRO.. CST 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 TOTA CLEVELAND 31 28 15 18 23 13 6 12 11 7 9 13 36 48 42 40 46 42 37 44 35 45 44 49 694 INDIANAPOLIS 33 17 19 15 15 20 4 10 3 7 6 5 10 29 35 21 31 24 24 31 28 41 31 38 497 MINNEAPOLIS 27 12 11 5 2 2 1 1 3 3 2 7 23 14 13 15 22 36 20 22 23 20 23 19 326 KANSAS CITY 30 3U 11 14 13 3 6 3 5 11 6 1 6 15 26 24 23 20 24 30 25 30 29 37 42? DENVER 19 16 11 5 4 1 7 11 9 13 8 3 3 6 6 8 6 27 28 27 14 14 21 21 288

TOTAL 140 103 67 57 57 39 24 37 31 41 31 29 78 112 122 108 128 149 133 154 125 150 148 164 2227
NUMBER OF DEPARTURES FROM MF1PHTS

AT GMT 1 2 3 4 5 ft 7 a 9 10 H 12 13 in 15 16 17 18 19 20 21 22 23 2t CST 19 20 21 22 23 24 1 2 3 t 5 6 7 a 9 10' 11 12 13 in 15 1ft 17 18 Tu TOTAI BOSTON U n n n n n n n n n l n 1 NEW YORK 1 C (i n n n l l n 1 1 1 1 7 WASHINGTON l 1 2 o n l l 1 l 5 3 3 11 23 JACKSONVILLE 1 1 n n n n n n n 2 2 1 5 1 3 n 2 18 MIAMI 1" u n n n n n n 1 2 n n 2 l n 7 CLEVELAND 1 n 1 1 1 i l 1 2 2 1 2 n 1 15 ATLANTA 4 3 4 l 1 1 1 1 3 a 5 8 7 9 5 9 a 9 11 a It 110 INOIANmPOLIS u u 2 1 l 2 3 2 1 4 4 2 5 2 5 it 5 43 CHICAGu u 1 2 1 3 2 1 5 1 1 it 5 2 l 1 30 MEMPHIS It 8 3 3 2 3 3 1 1 3 23 18 21 25 21 20 18 20 21 22 23 15 10 298

HOUSTOi.' 1* 1 2 1 1 1 1 1 2 1 it 3 5 3 2 2 3 2 5 3 5 52 MINNEAPOLIS n n n n n n n n n n 1 1 2 KANSAS CITY 4 2 14 l l 2 2 ft 5 5 3 5 7 It 6 5 4 1 67 FORT WORTH 3 2 1 l l 1 1 l l 2 7 7 5 8 2 5 6 2 5 3 8 72 DENVER u n n (1 n n n 1 n 1 2 ALbUQUcRQUE n n n n n n n 2 2 1 n 2 n n 7 LOS ANoELES 1 n n n n n n 1 1 n n 3 33 18 17 10 32 41 50 55 59 51 39 55 "60 56 61 44 39

NUMBER OF ARRIVALS AT MEMPHIS

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 CST 19 20 21 22 23 24 1 2 3 4 5 6 7 a 9 10 11 12 13 14 15 16 17 18 FRO . TOTAI BOSTON (1 n n 1 n 2 n 3 NEW YORK 1 1 2 n 1 2 7 WASHINGTON 1 I 1 2 2 4 5 4 1 3 2 1 3 1 1 5 37 JACKSONVILLE 1 2 1 1 2 1 1 3 1 1 2 16 MIAMI 1 n 1 1 n 1 2 6 CLEVELAND 1 1 1 1 1 1 1 1 1 2 1 1 13 ATLANTA 6 4 7 5 1 2 l 2 3 9 12 10 18 14 14 7 10 15 3 10 153 INUIAN.iPOLIS 2 4 3 3 1 1 n 1 n 5 a 7 3 4 4 5 2 4 4 ftl CHICAGO 2 1 1 "o n 2 1 2 1 1 2 2 1 2 1 19 MEMPHIS 11 13 6 4 4 3 1 3 2 2 20 19 22 26 17 25 22 15 21 27 19 16 298 HOUSTON 2 1 1 2 3 3 2 2 3 5 8 7 1 3 3 5 3 54 MINNEAPOLIS 1 n n n 1 n 2 KANSAS CITY 4 2 4 4 4 l 1 1 n l 3 3 2 5 3 4 2 5 2 51 FORT WORTH ft 3 1 2 n 3 5 in 5 5 4 4 7 10 7 2 5 5 84 DENVER a 1 n n n 1 1

" 1 4 ALBUQUERQUE 2 0. n 1 1 1 3 1 1 10 LOS ANoELES 1 1 l 1 n n 1 1 2 a

TOTAi. 36 35 21 19 16 17 5 5 4 2 9 31 49 58 67 • 59 68 60 47 59 59 49 51 826

NUMBER OF HANDOFFS TO MEMPHIS

FROM ATLANTA INUIANmPOLIS

HOUSTOu KANSAS CITY

FORT WORTH

AT G.JIT CST

1 2 3 4 5 6 7 a 9 10 11 12 13 14 15 16 17 18 19 20. 21 22 23 24

19 2U 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 TOTAI

26 18 13 12 12 4 1 3 1 2 2 7 15 25 21 27 33 29 27 23 35 26 34 22 418

10 14 4 8 8 2 3 1 2 1 2 3 12 25 14 11 21 14 5 16 14 15 12 217

5 5 6 1 3 5 2 n 1 n 1 2 6 4 9 8 a 7 10 5 5 7 ion

8 10 6 7 3 6 3 2 1 l 1 3 1 13 14 12 9 6 11 13 9 14 8 161 18 16 8 4 9 5 3 1 4 2 4 3 12 17 14 22 26 22 28 27 27 13 22 25 33? TOTAL 67 63 37 32 35 22 12 11 34 57 79 81 91 89 83 73 101 67 90- 74 1228
NUMBER OF DEPARTURES FROM HOUSTON

AT faMT CST

TO BOSTON

NEW YORK WASHINGTON

JACKSONVILLE

MIAMI CLEVELhND

ATLANTA INUIANmPOLIS

CHICAGu MEMPHli

HOUSTON

KANSAS CITY FORT WuRTH

GREAT I- ALLS UENVER ALBUQUcRQUE

SALT LmKE CY SEATTLL

OAKLANu

LOS ANuELES

fOTA^

1 2 3 4 5 6 7 8 9 19 20 21 22 23 24 1 2 3

1 1) n n

u 2 1 1 2 1 n l 3 1 5 l 1 3 u 3 l n

u n n n 4 i* u 3 2 1 n

u n n n n

1 2 n n 1 1 2 4 1 n 41 30 37 18 12 6 4 4 2 2 1 2 l n 7 a 4 5 10 2

u n n n n

1 u n n o n 2 u l n 2 n n n

u 1 n n

u 1 l l l 2 u 2 l 2 n

li 12 13 14 15 16 17 18 19 20 21 22 23 24

5 6 7 8 9 10 11 12 .13 14 15 16 17 18 TOTAI

n n n n n n 1 2

n 1 n 1 3 1 1 ? l 1 2 2 19

n 1 2 i n 2 1 n 1 1?

n 1 1 7 2 8 5 3 2 6 3 2 3 54

n 1 l 3 1 1 1 1 4 1 3 3 27

n n 1 n n n n n 1 n 2

l 2 4 3 l 1 3 5 4 6 1 3 3 51

n l n 1 n n 1 n n n 3

n 1 4 2 l l 2 1 15

n 1 2 5 2 10 4 4 1 3 7 3 1 2 54

2 5 27 65 Hi B5 94 83 73 81 6R 87 68 53 1026

n 1 3 2 1 1 1 1 1 2 3 3 27

l 9 11 14 23 15 23 10 22 18 21 19 11 234

n n n n n n 1 n n 1 n n n 1 3 2 1 1 n 9

n 1 n h 7 3 l 6 4 7 6 4 6 1 55

n n n n n n n n n 2

n n n n n n n n 1 n l 1 1 n l 1 2 n 11

1 2 l 4 2 3 4 l l 3 3 l 33

70 45 62 35 29 10 49 101 196 139 128 131 108 125 120 129 114 84 1638

NUMBER OF ARRIVALS AT HOUSTO

FROm

NEw YOkK WASHINGTON JACKSONVILLE

MIAMI CLEVEL«ND

ATLANTA INOIANmPOlIS

CHICAGu

MLMPHIb

HOUSTO,, MINNEAPOLIS

KANSAS CITY FORT WuRTH DENVER ALBUUUlRUUE

SALT LAKE CY SEATTLE

OAKLANu

LOS ANoELES

AT SMT 1 2 3 4 5 6 7 8 9 CST 19 20 21 22 23 24 1 2 3

2 3 n 3 1 1 2 2 1 n 3 1 2 1

1 1 1 n

n o 7 4 5 2 2 1 2

1 2 1 n

u 4 ? 7 3 3 1 1 3 1 57 44 37 32 23 10 6 3 5

u n

4 2 15 11 6 5 7 1 1 3

i 1 n 2 2 1 1 2 1 u [1 1 b 1 n

U 1 1 n 4 1 2 1 4

14 15 16 17 18 19 20 21 22 23 24

8 9 10 11 12 13 14 15 16 17 18 TOTAL

n 3 3 2 1 n 1 22

2 2 1 1 2 1 2 16

3 7 2 1 4 2 5 1 3 4 40

n 3 2 4 2 3 1 1 3 4 26

n n 1 n 1 ?

l 3 3 2 8 6 2 6 1 8 3 71

n 1 n 1 3 n 9

n 1 1 3 n n 1 12

2 3 4 4 2 3 l 3 3 4 ? 52 18 65 72 90 85 94 68 82 76 76 72 1026

n n 1 1 2 4 4 n 2 1 3 2 24 U 18 3 21 12 16 18 10 18 16 5 210

1 n 1 2 1 - n 7

1 1 2 3 6 2 3 4 33

n n n 1

TOTAL 106 78 58 47 41 19 21 33 17 100 125 121 135 102 119 113 126 105 1592

FRO,

AT 6mT CST220

5 23

NUMBER OF HANDOFFS TO HOUSTON

11

5 15

9 17

11 24

18

JACKSONVILLE

ATLANTA MEMPHIS

FORT WuRTH

TOTAL

27

3b 27 18 18

5

14

5

224

11

57 33

9 31

829

37 54 39 56 51 43 49 54

98 407
NUKbER OF DEPARTURES FROM MINNFaPOLIS

AT GMT 1 2 3 It 5 6 7 8 9 CST 19 20 21 22 23 24 1 2 3 TO BObTON n CI n NEW YOrtK 1 1 WASHlNoTON u n n JACKSONVILLE n n n CLEVELAND 2 5 l 1 n ATLANTh n n INDIANaPOLIS (1 n n n n CHICAGO 12 8 3 2 1 1 l l MtMPHIb U n n HOUSTO ,i n n n n n MINNEAPOLIS 10 y 10 lu 7 4 4 2 KANSAS CITY u n n FOKT WORTH u n n GREAT FALLS 1 l 2 l DtNVER l 1 n n n SALT L«KE CY l n n SEATTLt 1 ] D n n OhKLANo 1 n LOS ANoELES 1 1

•

l 12 13 It 15 16 17 18 19 20 21 22 23 24

5 6 7 8 9 10 11 12 13 14 15 16 17 18

TOTAl

n l n n f) n fl n n n 1 n l fl n 2 3 2 2 1 l 11

n n n n n n n 1 n 1 n 2

n n n n n n l fl n n n 1 l 4 5 2 2 l 4 5 5 l 2 2 2 46

n n l n n l n n n fl n n ?

n n n l n 1 1 fl 2 fl l 6 2 15 13 q in 15 15 9 11 16 12 11 13 13 193

n n n n f) l n n fl (1 n I 2

n n n n 1 n n fl n 1 a 23 51* 28 25 29 30 33 34 20 22 27 29 18 442

l 1 2 l n 2 5 1 n 2 1 1 1 18

n n n n 1 2 n fl n n 3

1 n 2 1 1 2 1 n 1 2 i 17

n 1 n n 1 1 n l n n n 2 a

n n 1 n n fl n l n n n n 3

n n n n 2 fl n n n l 5

n l n n 1 n n n n 3

n 2 n l l 2 l l 1(1 27 19 24 16 13 15 79 13 40 53 60 54 57 1*2 42 43 49 l»l

NUMBER OF ARRIVALS AT MINNFAPOLTS

AT GMT 1 2 3 4 5 6 7 a 9 10 ll 12 13 14 15 16 17 18 19 20 21 22 23 24 CST 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 in 15 16 17 18

FRO-. TOTA BOSTON 1 n n n n (1 n n 1 n n l n n n 3 NEW YORK 1 1 n (i n l n 1 n 2 l 8 WASHINGTON 2 u n n n n n 1 l n l 2 n n (i 7 JACKSONVILLE n n (i n n n n n 1 n n 1 CLEVELAND 3 1 1 1 n 2 1) n 1 n 6 8 3 3 4 7 2 4 5 2 56 ATLANTA u n (i n n n n n n n 1 n n (1 n 1 n 2 INDIANAPOLIS 1 1 n n n n n n n 1 (1 n 1 n 1 i 6 CHICAGO 6 12 10 16 li 5 3 Q 2 2 1 l 13 13 13 15 7 7 6 13 5 7 169 MEMPHIS 1 n (i n n n n n (1 n fl (1 (1 n 1 2 MINNEAPOLIS 19 11 9 10 12 9 2 i* 2 l 11 21 12 38 31 27 26 33 33 26 22 20 33 442 KANSAS CITY 2 u 1 fl 1 l n n 1 n 1 fl 2 1 11 FORT WORTH n a n n n (1 n n 1 n fl (1 1 n 2 GREAT FALLS 1 n 2 (1 n n 1 2 (1 2 1 1 n in DENVER 2 1 2 (1 n n 2 3 2 1 1 1 l 17 ALdUQUtRQUE u n n n n n n fl n n fl fl l 1 SALT LaKE CY 1 n n 1 n n fl 1 n 1 n n fl 4 SEATTLt i 1 2 (i n n 1 n n f) (1 ' 2 n n l (1 a OAKLAND 2 u 1 n n n n n n n (1 fl n n n fl 3 LOS ANoELES 1 n n n n n n n 3 1 n n 1 1 7

TOTAi. 39 27 22 33 25 15 14 22 49 6(1 60 44 50 51 52 41 42 40 49

NUMBER OF HANDOFFS TO MINNFAPOLTS

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 CST 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13. 14 15 16 17 18

FROn. TOTA CANADA 1 n fl n 1 (1 1 2 1 3 1 in CLEVELAND 1 1 l 1 1 fl 1 3 10 3 2 2 5 2 3 3 7 2 48 CHICAGO 17 14 18 13 12 7 2 3 4 3 2 5 7 17 23 16 19 17 15 15 14 17 23 283 GREAT FALLS 1 4 1 1 2 2 2 2 2 1 1 1 5 7 2 5 6 1 2 48 DENVER 4 1 2 2 1 1 1 n 1 4 1 2 3 5 1 2 3 34

23 19 23 17 14 13 34 27 25 31 30 20 24 24 27 30
NUMBER OF DEPARTURES FROM KANSAS CITY

TO BOSTON

NEW YOkK WASHINGTON JACKSONVILLE

MIAMI CLEVELAND

ATLANTA INDIANAPOLIS

CHICAGO MEMPHIb

HOUSTON MINNEAPOLIS

KANSAS CITY FORT WORTH

GREAT FALLS

DENVER ALBUQUtRQUE

SALT LAKE CY SEATTLt OAKLANu

LOS ANgELES

TOTAL

AT G.vlT 1 2 3 4 5 6 7 8 9 10 CST 19 20 21 22 23 21 1 2 3 4

J 1 1 1 n 2 2 1 2 1 2 1 n 2 U n

1 n n n

1 1 1 n 2 1 n 2 n

u n n 2 1 4 1 1 2 lb 5 8 6 2 2 It 2 2

4 1 5 l 4 1 1 1 n

u n n

1 u l 1 n 24 24 20 20 11 9 3 9 6 2

5 7 6 6 4 2 l 1 3

n n n n n n

1 3 2 3 l 1 2 1 2 n l n

1 n n n n n 2 1 l n n

1 1 1 n n n

1 1 l 2 l n l 69 44 49 47 27 19 12 16 10

11 12 13 14 15 16 17 18 19 20 21 22 23 24

5 6 7 8 9 10 11 12 13 14 15 16 17 18

TOTA1

n n l n n 1 n n n n 5

4 2 l 1 2 3 2 3 4 3 36

n 1 n 1 1 2 1 1 3 1 2 1 16

n l 1 n 1 1 1 n 1 n 7

n n 2 1 2 n 1 1 10

n n 1 3 2 3 2 2 2 20

l n 2 1 n 2 n 1 1 1 4 1 14

1 5 5 l 1 4 3 6 7 3 3 50

2 7 16 12 7 7 15 9 8 13 9 14 11 176

1 3 3 3 4 4 5 3 3 3 1 51

1 2 3 5 2 3 3 3 1 1 24

n 1 n n 1 1 n 2 1 2 11 7 36 38 44 43 43 43 32 46 52 50 34 30 626

1 3 3 7 3 4 6 9 9 a 13 10 9 120

n n (1 n n n n n 1 n 1 2 3 4 1 3 2 2 2 5 5 43

n n n 4 l 1 1 2 2 3 2 ? 2 26

n n n n n n n n 1 n n n 1 n n 1 6

n l 1 2 n 1 2 i 11

n n n 2 1 3 l 2 2 ' 4 2?

l 13 54 79 87 74 6P 80 74 86 106 91 87 75 1276 NUMBER OF ARRIVALS AT KANSAS CITY

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 CST 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 .14 15 16 17 18

FRO-, TOTAl BOSTON 1 n n t n 1 1 "n 1 2 6 NEW YOrtK 4 2 1 1 n n l 5 1 1 2 1 3 2? WASHINGTON 1 1 1 n 2 2 4 l 3 2 4 21 JACKSONVILLE 1 n n n 2 1 1 1 6 MIAMI 1 n n n 1 1 n 1 3 7 CLEVELAND 1 4 1 1 1 2 2 l 2 4 3 3 1 3 2 l 4 2 l 3 1 43 ATLANTA 1 1 1 n n l n n 1 1 l 1 1 Q INDIAN«POLIS 2 2 6 4 2 1 1 1 4 4 3 7 4 1 8 2 1 5 2 4 64 CHICAGO 12 a 10 9 7 7 2 2 l l ? 2 a 16 16 13 12 14 7 14 8 12 18 201 MEMPHIb 2 3 2 4 1 1 1 l 2 4 7 3 5 5 3 6 6 6 5 67

HOUSTO.. 1 4 3 2 1 2 l n 2 1 3 1 2 1 2 1 27 MINNEAPOLIS 1 1 3 1 1 4 1 3 3 18 KANSAS CITY 28 26 27 22 18 8 10 3 9 6 2 11 27 43 37 43 39 41 38 42 55 47 44 626 FORT WORTH 3 6 5 4 4 3 1 2 2 5 3 12 6 6 4 2 ? 8 3 10 91 DENVER 2 3 4 1 1 1 1 1 1 5 2 2 2 3 3 3 3 2 2 42 ALBUQUt-RQUE 1 1 1 1 n 1 2 1 4 3 2 2 6 1 26 SALT LAKE CY n n n n 1 n 1 SEATTLl 1 1 1 2 2 n 7 OAKLANij 1 1 1 n n 1 2 1 1 a LOS ANgELES 1 1 1 1 1 1 1 n 2 1 6 3 3 3 1 26

62 63 64 48 32 28 19 10 15 11 23 56 87 88 82 86 92 69 79 101 93 97 1318

NUMBER OF HANDOFFS TO KANSAS CITY

AT 6r>«T 1 2 3 4 5 6 7 8 9 CST 19 20 21 22 23 24 1 2 3

FRO,-, INDIANAPOLIS 10 6 11 4 7 4 i 1 1 CHICAGO 34 19 21 6 12 6 5 6 3 MEMPHIb 6 9 9 8 4 3 2 2 FORT woRTh 12 7 12 7 3 5 1 3 3 DENVER 10 10 9 4 3 2 1 11 ALBUQUlRQUE 3 1 2 1 3 1 75 54 64 3U 29 21

12

6

1 3

3

1

14 20 17 10 11 25

15 16 17 18 19 20 21 22 23 24

9 10 11 12 13 14 15 16 17 la

17 17 15 13 It 20 13

8 26 27 25 30 33 30 24 25 20 29 33 7 11 16 11 8 8 14 17 13 15 14 181 12 16 17 11 10 11 11 11 12 23 14 209

4 1 6 5 7 22 11 10 11 12 6 155

2 1 3 3 13 4 4 6 11 5 9 75 68 73 82 69 80 87 71 82 78 104 89 1262
NUMBER OF DEPARTURES FROM FORT WORTH

AT GMT 1 2 3 H 5 6 7 8 9 in ll 12 13 it 15 16 17 18 19 20 21 22 23 2t

TO CST 19 21) 21 22 23 24 1 2 3 t 5 6 7 R 9 10 11 12 13 it 15 16 17 1R TOTAl BOSTON U n

- n n n n n 1 n n n n n 1 n n 2 NEW YJkK n 2 l n n n n l 3 1 2 2 l t l 1 2 21 WASHINGTON 1 n 1 l n n n n 1 1 3 2 3 2 1 t 2(1 JACKSONVILLE 2 1 D n n n n n n 2 1 t 1 2 1 l 2 1 2 2tl MIAMI 1 0. l] (1 n n n n n 1 n (1 1 1 n n n n t CLEVELAND u n n n n n n n n n n n 1 n 1 n n n n ? ATLANTA 1 1 l n l n 3 l 3 l 6 1 6 3 3 l 1 2 i 36 INDIAN..POLIS 1 n 1 n n n n n n n 2 2 1 l 1 2 11 CHICAGO 1 l l 1 n n n 2 2 5 5 2 t 5 2 2 6 t 2 t5 MEMPHIS 3 1 n c 2 1 2 ? 6 fl 5 5 6 5 6 7 11 2 3 t 5 8t HOUSTON 10 6 5 h 3 3 3 1 1 10 16 13 7 19 It 19 It 16 13 12 7 12 210 MINNEAPOLIS n n n n n n n 1 n n n n 1 n n n n 2 KANSAS CITY 5 fa 3 1 3 3 1 1 t 5 fl 6 R 5 4 2 5 5 7 6 3 91 FORT wuRTH 23 Z

1-) lb 11 3 7 7 3 3 1 t 30 65 58 79' 76 63 58 83 78 78 59 ta 38 920 GREAT FALLS 1 n n n n n n n n n n n n n n 1 DENVER 2 2 it n 1 n n n 1 1 1 2 2 1 t 6 3 l ? 3? ALUUUUi-RUUE 5 5 2 l 2 1 n 1 8 7 t 3 3 7 6 5 12 16 8 5 101 SALT LAKE CY ll n n n n n n n n n 2 n n 1 n n 3 SEATTLc 1 n n f) n n n n l n n n n 1 n l t OAKLANu 1 o 1 (i n n n n n 3 l n l 1 n 2 n 3 i It LOS ANoELES 3 t 3 1 1 l n l l t 6 3 t 2 n t 1 5 6 ? 5? 58 50 30 23 18 10 58 inS 115 1?3 129 107 110 1 3t 13R 1 23 119 97 76 1675 NUMBER OF ARRIVALS AT FORT WORTH

AT GMT 1 2 3 t 5 6 7 r 9 in 11 12 13 It 15 16 17 18 19 20 21 22 23 2t CST 19 20 21 22' 23 2t 1 2 3 t 5 6 7 fl 9 10 ll 12 13 It 15 16 17 1R FRO- TOTA

NEW YOKK 3 n 11 tl n n n n n n n n n 2 2 1 n 1 1 n in WASHINGTON 1 1 1 1 n n n n l 2 2 1 3 2 2 1 l 19 JACKSONVILLE 1 2 n n n n n n n 1 1 1 2 1 1 1 t 1 16 MIAMI 1 1 n n n n n n n n n 1 5 1 n l in CLEVELAND J n n n n n n n n n l 1 n 1 1 2 6 ATLANTA 2 3 3 2 n n 1 2 l 1 2 3 1 2 2 l 5 31 INDIANAPOLIS 2 l (1 n n n n n 2 3 1 n 2 n 2 l 2 16 CHICAGO 2 2 2 2 1 2 n n 2 l l 3 2 5 2 2 2 5 2 5 t3 MEMPHIj 6 3 3 1 2 l l l 1 n l t 7 10 5 t 1 5 7 5 t 7? HOUSTON 15 8 6 6 3 13 l n a l 2 7 7 16 It 17 25 15 20 16 17 23 ?3t MINNEAPOLIS J fl n (i n n n n n n n 1 1 1 3 KANSAS CITY 9 10 6 8 t t 2 l 3 1 2 1 2 t 5 t 5 t 9 6 R It R 120 FORT WuRTri tl 3t 31 15 11 3 6 5 6 2 C 8 2t 55 59 55 91 59 63 an 80 76 65- 51 92n GREAT FALLS 11 (1 n n n n n n n n 1 n n n n n n 1 DENVER 1 5 2 n n n 1 n n l n 1 5 n 2 2 n 3 23

ALbUUUi_RGUE 3 5 3 2 3 2 n n 2 2 3 5 6 5 5 7 6 7 9 t 79 SALT L«K£ CY 1 1 n n n 1 n n n n n . n n n n l n t SEATTLE U 3 n n n l n n n n n ? n n l n 7 OAKLANu u 3 (1 n n n n n 1 n n n 2 1 n 2 2 l n 12 LOS ANgELES 7 2 2 2 1 2 2 1 t 3 n l 2 t 2 2 5 ? t tfl

93 76 62 39 27 28 11 10 12 7 It 33 71 87 9fl 139 ln3 119 125 137 139 123 lit 167t

NUMBER OF HANDOFFS TO FORT WORTH

AT GMT 1 2 3 t 5 6 7 fl 9 in 11 12 13 It 15 16 17 18 19 20 21 22 23 2t CST 19 20 21 22 23 2t 1 2 3 t 5 6 7 R 9 10 11 12 13 It 15 16 17 lfl FRO -i TOTA MEMPHIS 18 2u 15 10 t 11 t 2 1 l t 2 t 5 19 25 23 26 18 19 25 21 25 22 321 HOUSTON 17 19 12 12 11 13 1 2 3 1 2 5 13 2t 3t t2 31 35 2t 32 39 36 3B tt6 KANSAS CITY- 17 12 11 It 5 3 2 2 3 2 n 2 11 10 13 9 9 11 It It 2n 26 22 232 ALBUGUcRUUE 20 11 13 9 10 3 t 7 t 3 6 7 t 3 5 9 19 20 21 27 23 28 2t 15 295

72 62 51 t5 30 30 13 10 7 13 11 12 32 5fl HI 93 R6 85 8t 9t 108 111 97 129t
NUMBER OF DEPARTURES FROM GRFAT FALLS

AT GMT 1 ^ 3 4 5 MST 18 19 20 21 22

To CHlCAGo U n MINNEAPOLIS 1 u n n FORT AORTH n 6RLAT HALLS 3 5 7 5 49 DENVER II II SALT LAKE CY 2 SEATTLt. 1 1 1 1 LOS ANotLtS u (1 n

20

n

103

it in 12

12

5 13 14 15 16

n 1

n 1 n 2 i* 4 5

n n n

1 l n

1 n l

1 n n l

17 18 19 20 21 22 23 24

10 11 12 13 14 15 16 17

n n n 1 1 1 1 n 2 2 n n n n n n n 7 1 5 f> 8 7 6 3

2 n 3 3 1

1 n 3 1 1 1 l 3 3 1 n n n n n n

10

1 212

in

in

18

12 20 in 11

AT GMT 1 k 3 4 5 MST IB 19 20 21 22

FROi-i WAbHINuTON

CLEVELAND n CHICAGO u HOUSTOu 1 MINNEAPOLIS k 1 1 l 1 KANSAS CITY a 1 n FORT WORTH 1 n GRtAT PALLS 5 2 6 7 3 DENVER 2 1 1 1 1 ALbU0Ut_RuUE 1 u n SALT LmKE CY 1 SEATTLt- 1 1 2 OAKLANo u n LOS ANodLES u n

NUMBER OF ARRIVALS AT GREAT FALI S

8 9 10

17

11 12 13 14 15 16 17

4 5 6 7 8 9 10

1

17

19

12

17 -21 10 16 14 12 12

1

13

1 17

1

1 212

15

16

13

2

2 276

NUMBER OF HANDOFFS TO GREAT FALI S

FRO-.

AT GMT

MST

1 18

219

3 204 215 226 23

MINNEAPOLIS

DENVER

SALT LAKE CY

SlATTLil

6

13

2

4

13

1

3

13

1

6

12

1

121

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 TOTAI

1 1 2 2 2 5 3 2 1 4 2 2 1 48

n n 1 1 1 n 1 2 9

l 1 n 2 2 3 2 1 2 1 1 2 3n 4 1 l 1 2 10 9 5 l 3 5 2 3 R 68

12 17 12
NUMBER OF DEPARTURES FROM DEUVEP

TO BOSTON

NEW YOKK WASHINGTON

MIAMI ATLANTa INDIANAPOLIS

CHICAGu MtMPHIb

HOUSTOi. MINNEAPOLIS

KANSAS CITY FORT WJRTH GREAT rALLS DENVER ALBUQUcRQUE

SALT LmKE CT SEATTLE OAKLANu

LOS ANoELES

AT GMT 1 2 3 4 5 6 7 8 9 in MST 18 19 20 21 22 23 24 l 2 3

Q J n n n n

n n 1 n

n n o n

u n n n

u n n n

n a n n 4 2 2 l 1 l l U u 1 n n n n n n

I 1 1 n n 4 3 2 1 l 1 2 1 n 1 2 1 2 (1 n l n 17 It 11 12 9 6 2 3 l 1

1 2 It 1 1 n n

1 1 2 1 1 1 l

1 1 1 n 2 2 n 'n 3 1 2 n l

12 13 14 15 16 17 18 19 20 21 2? 23 24

5 6 7 8 9 10 11 12 13 14 15 16 17

TOTAl

1 n n n 1 n 3 2 n n n 7

2 n n 1 l 5

n n n l 1 n n n 1 n n n n n 1 2 4 4 2 2 4 4 6 4 2 l 4 55

1 1 n 1 n n n 4

l n l 2 n 1 2 7

2 n 1 l 2 2 l 2 n 2 17

1 4 4 l 1 4 4 3 3 3 1 42

1 2 l 2 2 2 1 5 23

l 1 2 1 n 2 l 15

6 12 24 20 23 IB 26 11 21 19 19 19 14 310

1 4 3 4 4 1 2 3 2 2 36

1 2 S 2 1 4 1 1 4 3 2 39

(1 2 1 1 n n 1 9

1 1 2 1 2 2 14

1 1 3 2 2 2 4 l 1 n 3 n 27 TOTAL 34 28 23 22 13 28 38 45 43 32 56 32 35 37 33 42 36

NUMBER OF ARRIVALS AT DENVER

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 MST 18 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

FRO.-. TOTAl BOSTON n n n n n n n n 2 n ?

NEW YOKK 2 1 n 11 n n 2 n l 1 n 7 WASHINGTON 1 n n n 1 n n n 1 l 4 CLEVELAND l n n n n n n 1 n 2 ATLANTA J 1 n n 1 n 1 n 3 INOIANrtPOLIS n n n n n n n n 1 CHICAGO 4 5 l 6 2 3 2 1 1 2 5 3 4 2 2 3 4 2 53 MEMPHIS U n G n n n 1 l 2 HOUSTO.i 1 1 n n n n 1 l 4 1 9 MINNEAPOLIS 1 1 2 n n r> 1 1 l 8 KANSAS CITY 4 5 3 1 2 4 1 1 n 2 4 1 l 2 3 l 2 4 43 FORT wuRTH 3 2 1 1 1 (1 l n n 2 3 2 2 1 4 5 3 32 GREAT l-ALLS 1 1 n n 2 n n 1 4 1 10 DENVER 19 Id 13 12 13 7 7 1 3 1 1 1 10 12 23 21 19 23 23 10 22 20 16 17 310 ALBUQULRQUE 3 4 5 3 2 1 l 1 1 2 1 2 2 2 3 33 SALT LaKE CY 1 2 3 1 1 1 1 l n 3 1 3 3 n 2 1 1 26 SEATTLt 1 1 2 n n 1 1 1 1 n 9 OAKLANo 1 1 1 2 1 n n 7 1 2 2 l 1 1 1 22 LOS ANuELES 3 2 1 2 1 2 n l 1 1 4 1 3 2 i 25

42 33 31 30 23 16 15 11 13 31 33 44 38 42 23 38 38 42 33

NUMBER OF HAMDOFFS. TO DENVER

FRO', CHICAGO MINNEAPOLIS

KANSAS CITY GREAT t-ALLS ALBUQUERQUE

SALT LAKE CY LOS ANuELES

1 2 3 4 5 6 7 A 18 19 20 21 22 23 24 1

26 20 12 12 4 5 6 2 2 1 1 3 1 1 13 12 10 4 3 2 3 2

1 1 n 20 10 9 9 2 5 4 1 11 10 8 5 5 6 9 4

12 11 4 8 7 4 2 14

in3

12

5

n 1

1 l 2 3 1 11 2 3 2 12 10 3 1 1 n

16 17 18 19 20 21 22 23 24 9 10 11 12 13 14 15 16 17 TOTA

23 20 14 17 14 17 12 16 21 276

2 1 2 2 22

12 13 5 7 13 7 11 6 14 147

1 2 1 3 10 10 7 10 6 4 3 11 12 6 138

11 28 29 18 13 10 15 18 14 234

4 11 22 22 13 20 23 13 13 231 TOTAL 85 65 44 41 21 22- 25 24 34 21 13 16 60 82 83 71 59 59 72 68 68 1058
NUMBER OF DEPARTURES FROM AL'IUOI IFRQIlE

AT GMT 12 3 MST 16 19 20 TO BOSTON

NEW YOiiK WASHINGTON JACKSONVILLE

MIAMI ATLANTA INDIANAPOLIS

CHICAGu MEMPHIS

HOUSTO,» MINNEAPOLIS

KANSAS CITY FORT WORTH GREAT FALLS DENVER ALBUQULRQUE

SALT LaKE CY OAKLAND

LOS ANGELES

TOTAL

5 6 7 22 23 21

n n

l

10

3

n n n n

n n

1 n n n n n n h

u n n n

1 l 1 1

n n n n n

3 l 1 l n n n n n

1 1 1 n 2 3 3 2 2 n

u n n n n n 1 6 1 l 1 l n l 9 18 6 5 8 5 l 2 2 2

1 2 n n n n 1 1 2 l n n 10 12 i 3 1 l

2 13 it 15 16 17 18 19 20 21 22 23 21

5 6 7 8 9 10 11 12 13 It 15 16 17 TOTA

n n n n n 1 n n n 1 n n n 2 n n n 1 n 5

n n n n 1 n n 1 n n L 1 n 1 1 l 5

n n 2 n 1 l n n 5

n n n n 1 n l n 2

n n n n 1 n n n n l 2

n 3 1 2 2 3 n 2 l 18

n n l l 1 1 2 i i 1 i in

2 2 2 6 i* 1 3 3 33

n n n n n 1 n n 1 1 l n 2 3 1 1 2 5 2 i 1 26

2 i 2 5 9 3 8 3 8 5 in 6 2 79

n n n n n n n 1 1 1 n 1 2 3 1 l l 3 1 1 33

1 12 31 11 25 23 22 27 36 31 23 13 319

1 n 1 n n 1 1 n n 7

1 n 2 l 1 it 1 3 1 n 5 28

1 n 9 5 10 5 3 1 6 6 10 10 111 31 12 26 11 16 8 15 59 68 51 11 13 57 62 58 16 12

NUMBER OF ARRIVALS AT ALRUOUFRQI IE

FROrt NEW YORK WASHINuTON JACKSONVILLE

MIAMI ATLANTA INDIANAPOLIS

CHICAGU MEMPHIb

HOUSTON KANSAS CITY FORT WORTH DENVER . ALBUQUtRQUE

SALT LaKE CY SEATTLE

OAKLAND

LOS ANuELES

AT GmT 1 2 3 1 5 6 7 8 MST 18 19 20 21 22 23 21 1

I n

(1 1 1 n n

1 n

1 2 1 n n 3 3 2 2 ln

1 1 n 2 3 1 1 1 1 5 3 7 2 2 3

1 1 3 1 1 1 16 10 12 11 7 8 1 2

1 1 n

1) n

1- 6 1 1 12 1 3 3 9 6 i 1

10

3 12 13

5 6

n

n

i 15 16 17 18 19 20 21 22 23 21

7 8 9 10 11 12 13 11 15 16 17 TOTAl

n 1 n n n n n 2

n n 1 -0 n n n n 1 n l 2 l n 6

n n n l 1 n 2 1 n n n 1

n 1 1 1 n n n n 8

n l n 1 1 1 3 3 2 ? 25

n l 1 1 n 1 3 n 7

l 7 1 5 3 3 1 5 in 7 55

n 1 1 2 1 1 3 1 26

3 8 1 5 3 1 10 3 12 15 11 101 i 2 2 2 1 3 1 2 2 i 2 36

8 30 13 21 21 21 25 31 29 32 319

n 2 1 1 2 n 8

n 1 2 2 n 1 6

n 2 1 1 1 3 3 23

2 6 7 1 6 12 9 6 5 10 111 TOTAL 11 33 30 27 22 19 11 « 21 52 70 12 19 61 55 71 72 61

NUMBER OF HANDOFFS TO ALBUQUERQUE

FRO,", HOUSTON KANSAS CITY FORT WORTH DENVER

LOS ANbELES

AT GmT 1 2 3 1 5 6 7 8 9 10 MST 18 19 20 21 22 23 21 1 2 3

1 n 5 3 3 7 1 1 2 2

19 15 16 11 11 5 8 3 3 1 6 7 6 8 5 3 1 2

21 8 8 8 8 6 7 7 1 3

12 13 11 15 16 17 18 19 20 21 22 23 21

5 6 7 8 9 "10 11 12 13 11 15 16 17

TOTAl

1 2 2 1 2 9

1 1 2 6 1 3 8 2 3 8 2 8 7?

1 2 13 16 11 25 20 23 19 21 13 30 27 317

1 1 3 6 5 7 15 18 7 12 10 9 136

3 1 1 16 11 16 15 18 26 18 13 16 217

TOTAi. 51 33 33 35 25 12 20 11 19 26 11 50 16 61 57 57 fil 56 62
NUMBER OF DEPARTURES FROM SALT I AKE CY

TO ATLANT«

CHICAGO

HOUSTON MINNEAPOLIS

KANSAS CITY FOKT WORTH

GKLAT FALLS

DENVER

ALBUQUi_RUUE SALT LAKE CY

SEATTLE. OAKLANO

LOS ANoELES

AT GmT 1 l 3 4 5 6 7 B 9 PST 17 la 19 20 21 22 23 24 1

l n n n

u n n

n l n n n

1 n

n n n n n

u n l

1 n n

l 2 2 i 1 l l o n l n 7 10 5 4 7 2 2 2 1

1 i 1 3 3 1 1 3 <* 2 1 1 2 l 1 2 n

11313

5

n

n

nn

n

l

nn4

n

n 1

It 15 16 17 18 19 20 21 22 23 21

6 7 8 9 10 11 12 13 14 15 16 TOTA

n n n n n n 1 n l 1 n 1 3

n n n n n n 1 a 1 1 n n n •1 n 1 n n n n 1 l a 1 l 1* l 2 n l n 6

2 2 2 3 2 3 1 l 26

(1 1 1 3 l 1 n n 8

1 10 6 9 12 13 16 15 13 9 14 168

a n 3 3 5 1 2 a 26

l l 1 2 1 4 1 1 3 1 3 31

n l 3 2 1 2 4 22 TOT« 11 21 11 16 8 21 17 30 Ifl 27 20 16 22

NUMBER OF ARRIVALS AT SALT LAKE CY

AT GmT 1 2 3 l» 5 6 7 8 9 10 ll 12 13 It 15 16 17 18 19 20 21 22 23 24 PST 17 18 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 FKOh TOTA1

NEi» YOkK 1 n n 1 n n n n n n n n n n 2 CHICAGO 1 l n n n 1 l n 4 HOUSTOn 1 1 n n n n n n n n ? MINNEAPOLIS l n n n n 1 n l 3 KANSAS CITY l n n n n n n n n n 1 FOKT viuRTH n n n n n n n n 1 2 3 GREAT FALLS u 1 l n l n 1 1 ? 2 10 DENVER 5 2 l 2 1 1 l 5 2 2 5 1 4 2 4 39

ALBUQUt-RQUE 1 1 1 n n n 1 1 1 1 n n 7 SALT LAKE CY 15 7 8 9 3 6 2 2 1 2 3 3 2 2 3 7 6 14 13 13 19 ll 10 168 SEATTLc 1 1 3 l* 1 1 1 l 1 2 2 5 n 1 3 30 OAKLANu 3 2 1 1 1 n 3 1 2 l ? 1 1 20 LOS ANbELES 2 2 1 2 n n 2 n 2 n 1 16 2b 11 16 18 13 12 16 16 14 22 17 16 29 22 17

NUMBER OF HAnDOFFS TO SALT LAKF CY AT GMT 1 <L 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 PST 17 18 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

FRO.i TOTA

GREAT FALLS 3 1 1 n 2 n 1 1 3 1 5 2 2 1 2 B 2 35 DENVER 21 17 12 13 9 2 4 2 2 6 3 4 1 2 9 7 17 18 14 3 B 17 14 11 216

SEATTLt- 4 1 5 5 1 1 1 1 1 1 1 5 5 11 5 2 2 2 2 3 2 61 OAKLAN.J 8 3 b 2 4 6 4 5 4 2 1 1 3 19 18 14 6 10 10 15 9 8 157 LOS ANbELES 1 2 1 5 4 2 1 n 1 5 3 1 3 1 1 1 1 33 37 24 24 25 18 8 10 10 21 32 56 42 25 18 22 37 35 24
NUMBER OF DEPARTURES FROM SEATTLE

AT GMT 1 PST 17

TO BObTOU

NL.v >ll..K WASHINuTON JACKSONVILLE

CHICAGO

HOUSTON MINNEAPOLIS

KANSAS CITY

FORT .voRTH GREAT KALLS OtNVER

ALBUOUtRQUE

SALT L/lKE CY StATTLL

OAKLAND

LOS ANoELES

TOTAL.

5 216 7 22 23

n 2 n n

n n n

n u n (l n n n

l u n 2 3 n

n n n

1 2 n

a n l

1 l l n 2 1) l

u 2 n n n

n n n i 4 2 a l 22 2a 16 is 15 19 16 21 21

fi 3 4 2 2 l 2

3 2 1 2 n n 1

11 12 13 m 15 16 17 18 19 20 21 22 23 24

3 4 5 6 7 8 9 10 11 12 13 14 15 16 TOTA

n n n n n o n n n 1 n n n 1 n n n n 3 n n 2 n n n n 7

n n n l 2 1 n n n n n 4

n n n n 1 n n n n n n 1 n n n 6 1 1 3 l 2 l 4 l 26

n n n n 1 n l n n n o ?

n n n n 2 n 1 n n l n fl n ? n 2 n n n 1 n l 7

n n n n 2 l n n n l n 7

n l n n 3 1 1 n n l 3 n 13

n l o l 1 l l l n 1 q

n n n n 1 3 2 n o n n n n 6

n 1 l 3 4 4 1 n 2 2 1 30 12 9 15 25 33 27 37 36 30 25 22 16 24 30 530

1 1 3 1 3 5 5 4 2 7 4 9 7 3 74

n n n 2 2 1 1 2 2 4 n 23

32 30 28 20 21 21 20 27 24 1R 13 12 20 31 50 55 52 44 39 40 31 35 40 37

MUMMER OF ARRIVALS AT SEATTLF

AT GirfT 1 2 3 4 5 6 7 R 9 10 11 12 13 14 15 16 17 18 19 20 21 2? 23 24 PST 17 lfl 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 FRO- TOTA BOSTON n n n n n 1 n 1 NLK YORK 1 I) n n n n n 1 n 2 WASHINoTOH U 1 n n n n n n 1 CHICAGO 1 1 3 1 l 1 i i 1 1 1 2 2 1 1 19 HOUSTON 1) l n n n n (1 n n n 1 MINNEAPOLIS 1 1 l n n n n 2 5 KANSAS CITY 3 l n n n l n 1 6 FORT WoRTri 1 1 1 n n 0- n l 4 GREAT HALLS 2 2 1 l n 1 1 1 1 l l 3 2 1 1R DENVER 1 2 1 n n 1 2 l 1 9 SALT L«KE CY 2 1 1 1 1 3 l 2 1 1 2 4 3 2 1 26 SEATTLE 3U 26 23 17 16 16 16 19 8 25 15 13 19 13 24 29 29 41 32 30 26 21 19 23 530

OAKLANi 4 i ? 5 4 2 l 1 n 3 7 5 5 3 3 3 3 3 57 LOb ANoELES 3 I 2 1 3 1 1 fl 1 2 2 1 1 2 -2 23

42 37 32 33 28 22 24 21 '20 14 24 33 38 53 46 41 32 31 29 32

NUMBER OF HANDOFFS TO SEATTLE

6RtAT hALi-S SALT LAKE CY OAKLAnU

AT GJIT PST

3195 6 7 B 9 10 n 12 13 14 15 16 17 18 19 20 21 22 23 24

21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 TOTA

4 2 1 n 2 2 1 n 1 1 1 4 5 1 1 4 3 2 51 4 4 2 1 l 1 2 1 3 5 2 1 5 2 3 46

3 3 1 l 1 l 1 5 8 10 5 3 2 5 5 5 80

10 11 14 11 11 10 17 15 14 10 10
NUMBER OF DEPARTURES FROM OAKLAND

TO BOSTON

NEW YOkK >ASHINoTON

JACKSONVILLE

MIAMI CLEVELAND

ATLANTn INDIANAPOLIS

CHlCAGu

HOUSTON MINNEAPOLIS

KANSAS CITY FORT WORTH

GREAT HALLS

DENVER ALBUUUtKQUE

SALT L«KE CY StATTLt

OAKLAND

LOS ANuELES

AT GviT 1 2 3 4 5 6 7 8 9 PST 17 la 19 20 21 22 23 24 1

n n n f) 1 a

0' n 2 2 3 1

u n 1 n n

I l n

n 1 n n

o l (1 n

l n n u l 1 n

1 a l 1 2 2 3

u 1 i n n n

1 n n n n n l

J n n

1 2 l

1 1 n 2 a l n

11

3 2 13 14 15 16 17 18 19 20 21 22 23 21

4 5 6 7 S 9 10 11 12 13 14 15 16

TOTAI

n n n 2 n n n 1 n n 3

1 n 2 6 5 2 2 3 2 3 1 36

n n n 1 1 n 2 n n 5

n n n 1 n n n 1 4

n n n 1 n n n n 2

n n n 1 1 n n 2 l n n 6

n n 2 n n n n l n 4

n n n 1 n n 3

n 3 1 4 1 3 2 2 4 2 2 38

n n 1 (1 l 1 2 1 1 n 2 in

n n n n 2 n n 3

n n 1 1 l l n 2 n l 8

n l 3 1 2 l n n 3 12

n n n 2 n n n n 2

n l 6 2 2 1 2 l l n l 1 22

n n 2 3 1 2 3 3 l 6 23

n 2 1 1 1 2 1 2 2 2 1 20

30 33 37

12 11 10 10 15 33 36 58 52 39 40 38 25 23 31 38

1 13 19 24 23 15 17 11 11 16 19 13 TOTAL 55 58 57 44 33 26 21 12 18 51 81 111 98 70 74 64 54 53 63 72 1131

NUMBER OF ARRIVALS AT OAKLANP

FRO.-. BObTON

NEW YOKK WASHINGTON JACKSONVILLE

MIAMI CLEVELAND

ATLANTA INOIANnPOLIS

CHICAGu

HOUSTOu MINNEAPOLIS

KANSAS CITY

FuRT WuRTH

DENVER

ALttUQUi-KuUE SALT LAKE CY SEATTLE OAKLAND

LOS ANoELES

TOTAi_

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 PST 17 18 19 20 21 22 23 24 1 2 3 4 5 6 7

2 1 n n n n n

1 1 1 2 2 2 n 3 1 2 1 n n r. n n n

1 O 1 n n n n

u 1 n n n n n n n

1 1 n n n n 1 n 2 n n l n n n

1) n n n n n n n n n n

1 3 2 2 2 2 n 2 3 n

1 2 1 2 n ? n

I) J 1 n n n r> n

I 2 2 1 n n n n

1 1 2 1 l n n n n n

1 2 1 2 n n n l 7 3 1 1 2 n n n n l n

4 2 3 4 1 l n l n 1 8 6 6 3 3 1 2 3 n 2 1 38 29 40 28 31 17 11 6 2 2 2 3 14 ?8

22 23 38 19 12 15 17 )3 2 2 3 1 1 3 77 80 103 63 56 42 32 23 6 7 11 2 11 16 33

16 17 18 19 20 21 22 23 24

8 9 10 11 12 13 14 15 16

TOTAI

1 O 1 O n 1 6

1 1 2 2 3 3 1 3 29

1 a 1 n n O 5

n n n n l 1 4

n n n n n 1 l 2 l n 7

n n n n n 1 4

1 n 1 n 2

1 4 n l 5 2 30

2 1 n 11

1 n n n l n 3

1 l 2 n 1 11

2 1 2 1 O a 2 14

1 2 1 n 1 2 14

1 2 1 1 2 2 2 2 28

2 2 1 3 1 3 1 1 31 4 3 7 3 4 1 8 4 5 74 43 40 66 36 43 36 25 27 30 597

6 16 10 14 15 17 18 15 15 297

66 95 65 74 63 61 61 63 1168

NUMBER OF HANDOFFS TO OAKLAND

AT GMT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 PST 17 18 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

FROi'i TOTA SALT LmKE CY 9 11 13 8 11 2 1 2 2 3 3 1 3 1 6 16 9 in 5 8 10 7 141 SEATTLc 4 7 4 5 3 5 1 3 1 1 4 5 7 6 3 4 7 6 7 11 94 LOS ANuELES 25 47 30 24 14 25 15 10 2 7 3 2 1 5 12 21 16 12 24 18 24 24 21 382 TOTAL 38 65 47 37 28 32 15 11 5 10 5 4 6 2 12 18 34 38 24 38 30 38 41 39 617
TO

AT bMT PST319

5 21

NUMBER OF DEPARTURES FROM LOS AtiGELFS

10

2 13

5 179

21

13 23 2415 16

BOSTON

NEW YO,<K WASHINGTON JACKSONVILLE

MIAMI

CLt«EL<J^ID ATLANTA INDIANAPOLIS

CHICAGu

MtMPHIS

HOUSTON MINNEAPOLIS

KANSAS CITY FURT WORTH GREAT FALLS DENVER ALBUQUcRQUE

SALT LAKE CY SEATTLt

OAKLANl LOb ANbELES

TOTA,_

1 n 3 n l n

J n l n n n

U (1 l n n 1 1 1 l 3 1

u n l n

n 2 n 2 1 I 1 5 1 5 1

CI n 1 n 1 n 2 i 3 2 n l

1 n n n 2 2 l n l 2 n 3 2 l 6 n 2 3

n n 1) n n n 3 2 2 n l n 5 3 4 a 5 3 l 1 l a 2 2 2 1 1 n 2 I 2 l 1 n n l 31 24 22 7 19 15 10 2 2 2

51* 54 b7 37 39 32 10 in 2 a

l l 7 3 2 4 3 2

n n 2 2 n 3 n 1 n 2 2 ? 3

n n 1 n n 1 n n

n 2 3 n 2 n l l

n 1 l 1 l n n

n n 1 l 1 n n 5 5 5 2 6 4 ? 5

n n l n 3 n 1 n l 3 2 l 4 2 3 2

n n 1 n n 1 1 n

l l 1 4 2 2 3 2 ? 2 3 2 5 2 4 2 4 5

n n 1 1 n n n n

? 1 2 2 4 3 ?

2 6 8 5 9 11 9 6 6 n

n n 2 1 2 1 l n n 2 2 1 1 n 4 2 2

4 9 16 10 13 IB 17 15 17 20 49 65 67 76 71 68 89 62 62 7fl

638

14

11317

5558

48

2 25

1111623 297

1035

103 93 95 59 67 62 41 23 17 IS 12 10 31 73 111 115 124 115 126 139 105 115 125 1783 NUMBER OF ARRIVALS AT LOS ANGELES

AT GMT 1 2 3 4 5 6 7 8 9 PST 17 IB 19 20 21 22 23 24 1 FROM BOSTON 4 1 n n n n

NErt YORK 4 3 1 WASHINGTON 4 n l n JACKSONVILLE 2 2 (1 l 1 2 7 MIAMI 1 n n n n CLEVELAND 2 1 2 2 ATLANTm l) 1 n inuianapolis u 2 1) n CHICAGu 1 a 1 3 4 2 2 2 MEMPHIS n 1 n n HOUSTON 4 4 1 2 l 2 MINNEAPOLIS 1 1 1 1 1 KANSAS CITY 2 1 3 2 1 3 FOKT WORTH 4 4 1 4 2 2 1 i: GREAT FALLS U n n n n DENVER 1 2 4 2 ALBUQUtROUE 8 11 9 11 8 3 l 2 i SALT LAKE CY 3 3 3 1 2 SEATTLE 2 3 1 1 1 2 OAKLAND 11 20 21 11 8 12 12 6 5 LOS ANuELES o5 64 57 42 40 42 24 16 7

13

5 15

7

6 17 18 19 20 21 22 23

8 9 10 11 12 13 14 15

n 1 2 n 2 n n (1 2 2 3 l l 2

2 1 1 1 l 1

n 1 1 2

1 n 1 n n 2 1 2 2 2

(1 n 1 n n n

1 n n n 1 1 4 5 3 3 4 4

1 1 n n 2 2 3 3 l 3

1 1 n 2 n

2 l 3 2 4 2 4 3 3 l 6 3

n n 1 n n

1 3 1 2 3 4 1 l 6 5 10 5 3 5 4 6

1 2 2 2 n

2 2 2 2 1 11 16 26 17 20 20 11 11 14 18

15 31 47 64 64 88 65 72 84 60 71

1022

1222

3 18

2

33

1022

52

2 27

1112223 276

1035

106 132 108 79 71 69 44 31 24 12 19 10 19 45 80 111 112 136 113 105 122 96 111 1764

NUMBER OF HANDOFFS TO LOS ANGELFS

FRO.. DENVER ALdUuUtRQUE

SALT LrtKE CY OAKLANJ

TOTAiAT 6MT PST

22

17

2 24

3 19

1010

319

5 21

8

14

12

723

12 13 4 5

81 65 42 50 34 25 20 20 12 15

15

7

20

10

3 28

19

11 21 22

13 14

109

23

15

9

16

813

1 23 49 61 57 53 56 40 51 43 45

TOTAL

233

251

47

343

874

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