What research is this? As far as I've been able to tell, CDC hasn't conducted a single randomized survey on any large group, but has only collected convenience

What research is this? As far as I've been able to tell, CDC hasn't conducted a single randomized survey on any large group, but has only collected convenience samples. Also keep in mind that due to compounding (keeping these people from infecting others on the plane and at home), the effect extends beyond the people prevented from traveling. You can also speculate that detectable infections are more transmissible during the journey.