Which is why work on fixing contrails is so important, it’d be insane to leave 50% improvement at a tiny cost unresolved whilst clawing back small percentage efficiency gains in co2 release from incremental and hideously expensive engine improvements.

We need to do both of course, but contrails should’ve been resolved the moment they were identified as so significant, it’s frustrating how slowly the industry responds to such an enormous opportunity (“we halved our climate impact last year” would be easy marketing)