The report quoted by Rivet seems classic science garbage to someone who works in veterinary epidemiology. This is just a study on the proof of principle that pigs could be infected and so they most probably used massive amounts of virus to cause the reaction, which would not be realistic in the field. The mention that infection can be caused without 'direct' contact is certainly not any indication of airborne infection - at very worst they are theorising that it could be transmitted by fomites - which is a very different risk to airborne.