An early measure to avoid the spread of COVID-19 has been the cancellations of flights from infected zones, e.g.: https://www.reuters.com/article/health-coronavirus-spain-flights/corrected-spain-cancels-flights-from-italy-for-two-weeks-in-a-bid-to-stop-coronavirus-idUSE8N29W006
(I wonder about the effectiveness, specificity, and sensibility of such measures, for instance, if I am a tourist that has been barely in contact with locals, it should be better to go back home, in isolation if necessary. But that is a different question)
However, surface connection has not been cancelled, and I could go back from Italy to Spain driving or by train. Also ships continue travelling, although maybe moving from Europe to US would not be that practical...
Is there a purely epidemiological reason why air transport is inherently more prone to contagions, or otherwise more dangerous? Or is it just that it is easier for a government to close airports than roads?