noun
Refers specifically to a large wide-body airliner, typically the Boeing 747. The term is a straightforward loanword compound.
成田空港でジャンボジェット機を見た。
I saw a jumbo jet at Narita Airport.
ジャンボジェット is a more common, shorter form without 機. ジャンボジェット機 explicitly includes the character for 'aircraft', making it slightly more formal or technical.
From English 'jumbo jet' combined with 機 (aircraft).