noun, noun or participle which takes 'suru'
emergency landing; forced landing; crash landing
Refers to an unplanned landing due to an emergency, such as mechanical failure, bad weather, or other in-flight problems. Used in aviation contexts.
エンジントラブルのため、飛行機は不時着陸した。
The plane made an emergency landing due to engine trouble.
Compound of 不時 (unexpected, emergency) + 着陸 (landing). The exact historical derivation is uncertain, but the components transparently combine to mean 'unexpected landing'.