Delta Air Lines

Scored 35 of 100 points, which is 35% and a band of 3 out of 5 (Middling).

Sustainable fuel in use: 0 of 18 points.
  Figure: 0.09% of fuel uplift.
  Why: Scored against 5% of fuel uplift for full marks. The global average is under 1%, so 5% is genuinely leading rather than arbitrary.
  Source: https://www.delta.com/us/en/about-delta/sustainability

Contrails and non CO2 warming: 0 of 15 points.
  Figure: not disclosed.
  Why: Around two thirds of aviation warming is not CO2, mostly contrails, and just 3% of flights cause 80% of contrail warming. Rerouting around the regions where they form costs roughly 1 to 4 euro a ticket, so an airline doing it is making a real choice. No other airline ranking scores this.
  Source: none recorded, so this measure scores zero rather than being estimated

Independent efficiency rating: 9 of 12 points.
  Figure: 59.7 of 100 points, class E.
  Why: atmosfair rates the 200 largest airlines on CO2 efficiency points from 0 to 100, covering about 92% of global traffic. It is the one figure here that does not come from the airline itself. No airline has yet reached class A or B.
  Source: https://www.atmosfair.de/wp-content/uploads/atmosfair-airline-index-2025-background.pdf

Fuel tankering: 0 of 6 points.
  Figure: not disclosed.
  Why: Carrying extra fuel to avoid buying it at the destination burns more fuel to save money. About one in five European flights involves some tankering, adding roughly 902,000 tonnes of CO2 a year across the continent.
  Source: none recorded, so this measure scores zero rather than being estimated

Science based target: 15 of 15 points.
  Figure: this airline holds its own validated target.
  Why: A target validated by the Science Based Targets initiative scores full marks. One held only at group level scores 12 of 20, because it is not a commitment this airline is held to.
  Source: https://sciencebasedtargets.org/target-dashboard

Net zero target: 3 of 5 points.
  Figure: 2050, published by the airline.
  Why: 2040 or earlier scores full marks, 2050 scores 3, later scores 1. A target the airline has not published itself, covered only by the IATA industry resolution, is capped at 1 because a trade body resolution is not a company commitment.
  Source: https://www.delta.com/us/en/about-delta/sustainability

Fleet age: 4 of 10 points.
  Figure: 15 years average.
  Why: Seven years or under scores full marks. A newer airframe burns materially less fuel, which is the single biggest lever an airline actually controls.
  Source: https://www.airfleets.net/ageflotte/Delta%20Air%20Lines.htm

CO2 per passenger km: 0 of 12 points.
  Figure: not disclosed.
  Why: 75g or under scores full marks. This is the only figure that compares two airlines like for like on the same route, and almost none publish it.
  Source: none recorded, so this measure scores zero rather than being estimated

Single use plastic: 4 of 4 points.
  Figure: Plastic cups eliminated across the network.
  Why: Eliminated scores full marks, reduced scores 6, a stated position with no detail scores 3.
  Source: https://trellis.net/article/inside-deltas-plan-to-take-single-use-plastic-cups-off-its-flights/

Onboard catering sourcing: 0 of 3 points.
  Figure: not disclosed.
  Why: Local or farm to table sourcing scores full marks. Hardly any airline discloses this, so it separates the ones that have actually looked.
  Source: none recorded, so this measure scores zero rather than being estimated

Scoring zero for want of a sourced figure: Contrails and non CO2 warming, Fuel tankering, CO2 per passenger km, Onboard catering sourcing.