The best KO method is to just chase it down riding a griffin, which is the only vanilla flyer that you can use weapons while riding. Alternatively you can "ride" a wyvern by standing on its back without actually mounting it and using whistle commands, you can also mount a tapejara's passenger seat and do that without the slight risk of falling like with a wyvern. Another alternative is to have a friend carrying you with a stamina leveled pteranodon (argentavis might work but it's a bit slow), but be careful not to accidentally shoot your pteranodon!