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to jump up; to start up; to leap to one's feet; to fly away; to take off
鳥が空へ飛び立った。
The bird took flight into the sky.
飛行機が滑走路から飛び立っている。
An airplane is taking off from the runway.
巣から飛び立つ雛鳥を見守った。
I watched over the fledgling bird taking flight from the nest.