AIRE, a town of north France, on the Lys, in the department of Pas-de-Calais, I 2m. S.S.E. of St. Omer by rail. Pop. (1931) 7,538. The town lies in a low and marshy situation at the junction of three canals. In the middle ages Aire belonged to the counts of Flanders, and a charter (1188) is still extant. It was given to France by the Peace of Utrecht 0713). The church of St. Pierre (i 5th and i6th centuries) shows three stages of Gothic architecture. The hotel-de-ville is i8th century. Aire has considerable trade in agricultural produce. In the World War it was one of the headquarters of the British Army (1917-18).