The Daily Flight Time Index:
A NAS Performance Metric
Mark Hansen
Kam Shing Leung
April 3, 2003
1
What is the DFTI?
4
4
4
A Daily Performance Metric
Measures Daily Variation in Flight Times
Measure Daily Variation in Flight Time
Components:
ƒ
ƒ
ƒ
ƒ
Departure Delay
Taxi-Out Time
Airborne Time
Taxi-In Time
2
What is the DFTI?
4
4
4
A Weight average flight time
Weights are constructed to maintain day-to-day
comparability
DFTI controls for:
ƒ
ƒ
Changes in schedule padding
Changes in city-pair distribution of flights
3
Daily Flight Time Index, 1995 to 2002
with 365-Day Moving Average
180
Daily
365-day average
170
DFTI (min)
160
150
140
130
120
Jan-95
Jan-96
Jan-97
Jan-98
Jan-99
Jan-00
Jan-01
Jan-02
Date
4
30-Day Moving Average of DFTI, by Season
1995 to 2002
150
30-Day Moving average of DFTI (min)
145
140
135
130
125
Jan-95
Jan-96
Jan-97
Jan-98
Jan-99
Jan-00
Jan-01
Jan-02
Date
5
How is the DFTI constructed?
4 steps
4 Identify city pairs
4 Compute city-pair weights
4 Compute Daily Average Flight Time (DAFT)
by city-pair
4 Compute DFTI and its components
6
Step 1:
Identify City Pairs
4
4
4
4
4
Data from Jan 1, 1995 to Dec 31 2002 included
33 days dropped due to low city-pair
representation
At least one completed flight on every day
remained
776 city-pairs with more than 7000 daily flights
Can increase city-pair representation by
dropping more days and vice versa
7
Step 1:
Days included vs. ODs available
900
877
(40 days dropped)
852
800
841
816
802
776
793
783 777 776
(33 days dropped)
720 719
700
697
OD appeared in all days
672
642 639
600
604
569 568 568 568 568 568 568 568 568 568 568 568 568 568 568 568 568 568
525
500
511
492 485
400
300
231
200
130
100
2881
(1 days dropped)
2886
2891
2889
2896
2901
2906
2911
2916
2921
Days included (out of 2922)
8
Step 2:
Compute City-Pair Weights
Fi
Wi =
∑ Fj
j∈CP
Wi
- Weight for city-pair i
Fj
- Flights for city-pair j during study period
CP
- Set of city-pairs in the DFTI
9
Step 3:
Compute Daily Average Flight Time
4
4
Flight Time Defined as Total Time from
Scheduled Departure to Actual Arrival
Flight Time is the sum of four components
ƒ
ƒ
ƒ
ƒ
Origin delay (against schedule)
Taxi-out Time
Airborne Time
Taxi-in Time
10
Step 3: compute DAFT
location
Flight Time and Its Components
Dest. Gate
Dest. Runway
Origin Runway
Origin Gate
time
Scheduled
Departure Time
Actual Departure Wheels-Off Time
Time
Wheels-On Time
Actual Arrival
Time
11
Step 3:
DAFT Calculation
f—Flight index
i—City-pair index
d—Day index
DAODid =
∑ OD
f ∈S id
N id
Origin Delay
DAFTid =
f
DATOid =
∑ TO
f ∈S id
N id
Taxi-out Time
∑ FT
f ∈S id
Sid—Set of flights for citypair i on day d
f
Nid—Number of flights in
Sid
N id
f
DAABid =
∑ AB
f ∈S id
N id
Airborne Time
f
DATI
id
=
∑ TI
f ∈ S id
f
N id
Taxi-inTime
12
Step 4:
Compute Daily Flight Time Index
4
Weighted average of DAFTs
4
Weights obtained as explained above
4
Overall DFTI and its components calculated in
similar manner
13
Step 4:
DFTI calculation
i—City-pair index
DFTI id =
d—Day index
DODI d =
∑ W ⋅ DAOD
i∈CP
i
Origin Delay
id
DTOI d =
∑W ⋅ DAFT
i∈CP
∑ W ⋅ DATO
i∈CP
i
Taxi-out Time
CP—Set of city-pairs in
the DFTI
id
i
id
DABI d =
Wi—Weight for city-pair
i
∑ W ⋅ DAAB
i∈CP
i
Airborne Time
id
DTII d =
∑W ⋅ DATI
i∈CP
i
id
Taxi-in Time
14
Daily Origin Delay Index, 1995 to 2002
Daily Taxi-Out Index, 1995 to 2002
with 365-Day Moving Average
50
with 365-Day Moving Average
24
Daily
Daily
365-day average
365-day average
45
22
40
20
35
DTOI (min)
DODI (min)
30
25
18
16
20
15
14
10
12
5
0
Jan-95
Jan-96
Jan-97
Jan-98
Jan-99
Jan-00
Jan-01
10
Jan-95
Jan-02
Jan-96
Jan-97
Jan-98
Daily Airborne Index, 1995 to 2002
Jan-00
Jan-01
Jan-02
Daily Taxi-In Index, 1995 to 2002
with 365-Day Moving Average
110
Jan-99
Date
Date
with 365-Day Moving Average
9.5
Daily
365-day average
109
9
108
8.5
107
8
DTII (min)
DABI (min)
106
105
7.5
7
104
6.5
103
6
102
Daily
101
100
Jan-95
5.5
365-day average
Jan-96
Jan-97
Jan-98
Jan-99
Date
Jan-00
Jan-01
Jan-02
5
Jan-95
Jan-96
Jan-97
Jan-98
Jan-99
Date
Jan-00
Jan-01
Jan-02
15
365-D ay M oving Average of D FTI and C omponents
1995 - 2002
1 60
1 40
1 20
D FTI (m in)
1 00
T axi-In
A irborne
80
T axi-O ut
O rig in De la y
60
40
20
0
J an-96
J ul-9 6
Jan-97
Jul-97
J an -9 8
J ul-9 8
J an-99
J u l-99
J a n-0 0
J ul-00
Jan -0 1
J ul-0 1
J an-02
J u l-02
D ate
16