Energy intensity of passenger air travel and freight
3.8 A closer look at the weight share of freight in passenger aircraft
haul47 scheduled passenger services, 10% in international short/medium haul48 scheduled passenger services and around 4% in domestic scheduled passenger services [AEA 2001]. In Japan, All Nippon Airways report the weight shares of freight in their passenger aircraft at 13% on domestic routes and at 36% on international routes [All Nippon Airways 2000b]. These data suggest that, as a general rule of thumb, Asian carriers transport the highest shares of freight in their passenger aircraft while the US passenger airlines transport a lower share of freight than the European passenger airlines do. This is probably due to the large share of domestic traffic performed by the US air carriers that accounts for around two-thirds of all the RTKs and about three fourths of all the RPKs [DOT 2000, p. 323].
Generally, the overall statistics mentioned above suggest that the freight share is higher in long-haul traffic than in medium-haul and short-haul. A look at some statistics on the freight weight shares in individual aircraft confirms this picture, see Table 3.10.
As was touched upon briefly in Section 3.7 the airlines use different methodologies for the allocation of their fuel consumption on passengers and freight. Most airlines attribute all the fuel consumed to their passenger services. Some airlines attribute the same amount of fuel to a tonne of freight as to one tonne of passenger weight (including their baggage). Other airlines multiply the passenger weight with a factor of between 1,4 and 2 to account for the weight that is attributable to a number of in-flight passenger services (see Section 3.7 for a further description of this issue).
47 AEA longhaul is the sum of traffic between Europe and North Atlantic, Mid Atlantic, South Atlantic, Sub-Saharan Africa, Far East/Australasia and other long haul routes [AEA 1999, 2000c and 2001].
48 International short/medium haul is the sum of traffic between countries in Europe and between Europe and North Africa and the Middle East [AEA 1999, 2000c and 2001].
US air carriers 1998-1999-2000
All Nippon Airways 1999
Lufthansa 1990
Avr. Passenger aircraft only
Passenger aircraft only Passenger aircraft only
B747-100 11%
B747-400 25% 16% (domestic only) 38%
B747-200/300 22% 29%
B-777 36% 13% (domestic only)
DC-10-40 18%
DC-10-30 30% 38%
MD-11 39%
A310 29%
A300-600 19% 32%
B767-300ER 37% 12% (domestic only)
B767-200ER 26% 11% (domestic only)
B757-200 13%
B727-200 4% 11%
MD-80/90 4%
A320-100/200 6% 4% (domestic only) 9%
A321 6% (domestic only)
B737-300 4% 10%
B737-1/2/4/5/800 3% 8%
DC-9-30/40/50 4
F-100 2%
Table 3.10: Estimates of the freight weight as percentage of the total revenue weight in passenger aircraft
It should be noted, that these freight weight percentages are calculated (by the author of this report) on the basis of data for the cargo payload in tonnes as well as the passenger load factor and the average number of seats in different passenger aircraft for the United States air carriers 1998-2000 and for All Nippon Airways in 1998 and for Lufthansa in 1990. These factors may change from year to year and are different from airline to airline. The estimates for the average over each model for the US air carriers (Column 2) is for all aircraft, not only passenger models, and may include some all-cargo models
Sources: [Air Transport Association 1999, 2000e and 2001], [All Nippon Airways 2000b] [Reichow 1990 and 1992].
The average revenue of the World’s airlines per tonne of freight is around 60% lower than the average revenue for a tonne of passengers (see Table 4.3 in chapter 4) [ICAO 1996c and 2000d]. We argue that this factor should also be taken into account in a discussion of which methodology that could potentially be used for the allocation.
Therefore, if the fuel is distributed between freight and passenger loads according to their revenue shares, the weight of the passengers should be multiplied by a factor of around 2,5.
LONG HAUL B-747 Factor
pass:freight
Fuel per RPK [g]
Fuel per RFTK [g]
Total fuel per aircraft km [kg]
All is allocated to passengers 1:0 46 (48) 0 (0) 12,6 (12,9) Equal weight distribution 1:1 35 (31) 349 (315) 12,6 (12,9) Correction for the weight of
in-flight passenger services
1,7:1 39 (37) 228 (216) 12,6 (12,9)
Distribution according to the revenue per tonne
2,5:1 41 (40) 164 (159) 12,6 (12,9)
Table 3.11: Comparison of the fuel that is attributable to freight and passengers in a B747-400 on a long-haul flight when using the four different allocation methodologies
The figures outside the brackets are for an average B747-400 that is operated by the US air carriers. The freight weight is 9 tonnes, the aircraft accommodates 376 seats, the passenger load factor is 72%, 271 passengers are onboard and their weight (inclusive baggage) is 27 tonnes. Thereby, the freight weight share is 25%.
The figures in brackets are for a B747-400 operated on long-haul routes by Lufthansa in 1990. The freight weight is 14 tonnes, the aircraft accommodates 384 seats, the passenger load factor is 70%, 269 passengers are on-board and their weight (inclusive baggage) is 27 tonnes, the freight weight share is 35%)
Sources: [DOT 2001], [Air Transport Association 1999, 2000e and 2001] and [Reichow 1992].
The four different methodologies for distributing the fuel between freight and passengers are illustrated in Tables 3.11 and 3.12 and Figure 3.11. Not surprisingly, the most extreme difference in the estimate for the specific fuel consumption per revenue passenger kilometre appears between the methodology where all the fuel is attributed to passenger transport and the methodology where the fuel is distributed evenly between passengers and freight on an equal weight basis. In the latter case the specific fuel consumption per RPK is reduced by around 24-35% for long-haul trips in a B747-400 and by around 5-13% on medium-haul trips with B757s and A320s. The implication of this finding is that the figures for the specific fuel consumption of aircraft and airline operations that includes the fuel which is attributable to freight (for example those figures that are shown in Figures 3.6, 3.8, 3.9 and 3.10) would typically be reduced by 5-13% on medium range and by 24-35% on long-haul. We note that these are rough estimates and may differ between airlines and between different types of aircraft (see Tables 3.11 and 3.12 and Figure 3.11)
MEDIUM-HAUL B-757 and A320
Factor pass:freight
Fuel per RPK [g]
Fuel per RFTK [g]
Total fuel per aircraft km [kg]
All is allocated to passengers 1:0 38 (38) 0 (0) 5,0 (3,8) Equal weight distribution 1:1 33 (36) 329 (361) 5,0 (3,8) Correction for the weight of
in-flight passenger services
1,7:1 35 (37) 204 (217) 5,0 (3,8)
Distribution according to the revenue per tonne
2,5:1 36 (38) 143 (149) 5,0 (3,8)
Table 3.12: Comparison of the fuel that is attributable to freight and passengers in B757-200s and A320s operated on medium-haul distances when using the four different allocation methodologies
The figures outside the brackets are for an average B757-200 that is operated by the US air carriers. The freight weight is 2 tonnes, the aircraft accommodates 186 seats, the passenger load factor is 71%, 132 passengers are onboard and their weight (inclusive baggage) is 13 tonnes. Thereby, the freight weight share is 13%.
The figures in brackets are for an average A320 that is operated on medium-haul routes by the US air carriers. The freight weight is 0,6 tonnes, the aircraft accommodates 148 seats, the passenger load factor is 68%, 101 passengers are on-board and their weight (inclusive baggage) is 10 tonnes, the freight weight share is 6%)
Sources: [DOT 2001] and [Air Transport Association 1999, 2000e and 2001].
The selected aircraft shown in Figure 3.11 are arranged with the most fuel-efficient aircraft, measured in fuel consumption per RTK, on the left hand side of the figure. The B767-300/300ER is the most fuel efficient when considering the fuel consumption per RTK and therefore also per RPK when distributing the fuel consumption on an equal weight basis between passengers and freight (methodology 2). The relative difference between the specific fuel consumption figures of methodology 1 and 2 is greatest for the MD-11s, the B767s and the B777s. For these aircraft RPK2 is between 35-38%
smaller than RPK1. For the DC-10s, the 747s, the B767-200s and the A300-600s RPK2 is between 18-30% smaller than RPK1. That is, if comparing the specific fuel consumption figures of these long haul aircraft to the most fuel-efficient medium haul aircraft (B757-200s, A320s and B737-800s) they are at level or even more fuel-efficient if using methodology 2.
Figure 3.11: The variation in the specific fuel consumption per RPK when using four different methodologies for attributing fuel to freight
RPK1 represents the methodology where all the fuel is attributed to passenger transport.
RPK2 represents the methodology where the fuel is distributed equally between passengers and freight on a weight basis. RPK3 represents the methodology where the weight of the passengers is multiplied by a factor of 1,7 before distributing the fuel consumption between the weight of passengers and freight. RPK4 represents the methodology where the weight of the passengers is multiplied by 2.5. The examples here are for selected aircraft operated by American air carriers in 1999. The average passenger loads factors as well as the average freight weight may vary considerable between airlines and may change from year to year.
Sources: Fuel consumption from [DOT 2001] and freight loads from [Air Transport Association 1999, 2000e and 2001].