noun
stratoplane
Historical term for a hypothetical high-altitude airplane designed to fly in the stratosphere.
成層圏飛行機は、かつて構想された高高度飛行機の一種だ。
The stratoplane is a type of high-altitude aircraft that was once conceived.
Compound of 成層圏 (stratosphere) and 飛行機 (airplane). The exact historical origin of the term is uncertain; it likely emerged in early aviation literature.