Studie zeigt: Maskenpflicht auf Langstreckenflügen verhindert Übertragung von SARS-CoV-2

It seems like they are only comparing case counts with flight duration, and they never directly compare masked to unmasked flights:

>Compared to short flights without masking, medium and long flights without masking were associated with 4.66-fold increase (95% CI: [1.01, 21.52]; p < 0.0001) and 25.93-fold increase in incidence rates (95% CI: [4.1, 164]; p < 0.0001), respectively; long flights with enforced masking had no transmission reported. A 1 h increase in flight duration was associated with 1.53-fold (95% CI: [1.19, 1.66]; p < 0.001) increase in the incidence rate ratio (IRR) of cases. Masking should be considered for long flights.

Not sure how you get from that to the conclusion that enforced masking is effective. Yes, they mention that long flights with masking had no transmission, but there is no statistical test for this which makes me very suspicious that it is a low N that wouldn’t pass the test.