Number + 架 + Aircraft Noun
架 (jià) is the measure word (classifier) used for counting airplanes, helicopters, and other aircraft. Like all Chinese measure words, it must appear between a number and the noun it modifies. For example, 一架飞机 means 'one airplane.'
天上飞过两架直升机。
Tiānshàng fēiguò liǎng jià zhíshēngjī.
Two helicopters flew across the sky.
机场停着好几架飞机。
Jīchǎng tíngzhe hǎo jǐ jià fēijī.
Several airplanes are parked at the airport.
他们派了三架运输机运送物资。
Tāmen pài le sān jià yùnshūjī yùnsòng wùzī.
They dispatched three transport planes to deliver supplies.