What the evidence says
Contrails are just water vapour.
Contrail cirrus is the largest single contributor to aviation's warming effect: 57% of its net effective radiative forcing in 2018 (best estimate, low confidence; Lee et al. 2021).
SAF will fix aviation's climate impact.
At the EU's 6% mandate, about 94% of jet fuel burned in Europe in 2030 is still fossil. Contrails need their own lever.
Rerouting solves contrails.
It works for a well-forecast few. The largest planned European programme would reach about 0.05% of annual flights (CirculAIRity calculation).
Cleaner engines will solve it.
Lean-burn engines cut soot about a thousandfold, yet contrail ice stayed high (Voigt et al., Nature, 2026).
Contrail avoidance is almost free.
Every diversion burns extra fuel: a certain CO2 cost against an uncertain contrail benefit, and blocking flight levels cut sector capacity by at least 20% in simulation (EUROCONTROL MUAC 2024).
You can't regulate what you can't measure.
The EU has monitored non-CO2 effects per flight since 1 January 2025.
Others are saying it too
Jet Zero Taskforce
Rerouting is “not currently achievable in busier, more complex environments”; standard metrics are needed.
VoiceTransport & Environment
The EU's first monitoring scope ignored about two-thirds of Europe's contrail impact.
VoiceeasyJet, Ryanair and Wizz Air
“We absolutely cannot end up with a blank dataset” for long-haul flights.
Lee et al. (2021)
Aviation is warming the climate “at approximately three times the rate of that associated with aviation CO2 emissions alone.”