Peinador Airport (Vigo) is the closest one. It connects with the most important spanish cities and has international flights too. It is 50 kilometres far by road from A Guarda. There are two more airports, both in A Coruña province: Alvedro Airport (A Coruña), and nearer, 150 kilometres, Lavacolla Airport (Santiago de Compostela).
Due to A Guarda location in the border with Portugal, the Sa Carneiro Airport in Porto, just 100 kilometres far, is another interesting option to get to A Guarda.