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energy efficiency coefficients – i.e. for the aircraft fleet of a specific geographical zone, taken
as whole – and (ii) their corresponding energy efficiency gains. Both are obtained based on
empirical data obtained from the IEA and the ICAO. Energy efficiency coefficients and their
evolution rules (i.e. energy efficiency gains) until 2025 are obtained by directly comparing the
evolution of jet fuel consumption (taken from IEA data) and air traffic (taken from ICAO
data). Figure 3 illustrates this approach 21 .
Jet fuel (Mtoe)
250
200
150
100
50
0
1983 1987 1991 1995 1999 2003
1000
750
500
250
Jet fuel (IEA data) Air Traffic (ICAO data)
0
Air traffic (10 9 ATK)
EE coefficient
(10 −7 ktoe.ATK −1 )
5
4
3
2
1
0
1983 1987 1991 1995 1999 2003
Figure 3: Jet fuel consumption (Million Tonnes of Oil Equivalent (Mtoe)), Air traffic (ATK,
billions) and Energy Efficiency (EE) coefficients at the world level. Illustration of the approach
used to compute EE coefficients and their yearly growth rates (i.e. energy efficiency gains)
for the aviation sector.
Source: Authors, from ICAO and IEA data.
These results are commented in Chèze et al. (2012) and summarized in Chèze et al.
(2011). We thus only present here the main conclusions, i.e. the three “Traffic efficiency
improvements” scenarios. These scenarios are defined according to the following results on
[air traffic] energy [efficiency] gains: (i) some regions are more energy efficient than others,
and (ii) regions do not encounter the same energy gains. By combining the current energy
21 In Figure 3 (left panel), the dotted black line represents air traffic (expressed in ATK) and the solid black
line represents jet fuel consumption (expressed in Mtoe) for a given region. As explained in Chèze et al. (2011,
2012), energy efficiency coefficients for each year may be obtained by computing Mtoe/ATK (right panel),
where ATK means “Available Tonne kilometre”. Thus defined, Energy Efficiency (EE) coefficients correspond
to the quantity of jet fuel required to power the transportation of one tonne over one kilometre. For a given
regional aircraft fleet, EEt+1 < EEt means that quantities of jet fuel required to power the transportation of
one tonne over one kilometre have decreased. Thus, a negative growth rate of EE coefficients, as it is expected,
indicates the realization of energy efficiency improvements in air traffic for the region under consideration. As
it may be deduced from the illustrative Figure 3, EE coefficients negative growth rates arise when, in a given
year, jet fuel consumption growth rates are slower than air traffic ones.
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