That does not jibe with my reading. Which is that there were certainly flightless birds that survived K-Pg (Palaeognathae, ostrich ancestors) and the dominant f

That does not jibe with my reading. Which is that there were certainly flightless birds that survived K-Pg (Palaeognathae, ostrich ancestors) and the dominant flying dinosaurs (Enantiornithes) died off, but Neognathae survived and was flight-capable.