、。
Two planes, one large and one small, were parked inside the hangar.
Literal
Large [and-と] small [possessive-の] two [counter-台] [possessive-の] airplane [subject-が], hangar inside [at-で] was-stopped-[polite-ました].
A noun-phrase-heavy subject: 大型と小型の2台の飛行機 stacks two attributive の particles to express 'two planes, one large and one small.' 台 is the counter for vehicles and machines. ~ていた on a change-of-state verb like 停止する describes the resulting state rather than the action itself — here the planes were in a parked/stopped state, not in the act of coming to a stop. 内 used as a suffix on a noun means 'inside' (somewhat literary compared to の中).