。
Reportedly, a civilian aircraft violated a military zone.
Literal
Civilian-aircraft [subject-が] military's territory [object-を] violated [reportedly-とのことです].
とのことです is the reported-speech frame — 'it is said that,' 'I hear that,' 'reportedly.' Used to attribute the information to some other source, often a news report or hearsay. Built from the quotative と + のこと + copula: 'the matter (cited) as X.' 民間機 is the civilian-plane counterpart to 軍用機 (military aircraft).