登机
dēng jī · HSK 7
to board a plane
✈️ deng = ascend/step up + ji = machine — you step up onto the machine
登 means to climb or ascend (like 登山 = climb a mountain). 机 means machine (as in 飞机 = flying machine = airplane). Boarding is literally ascending onto the machine.
登 — 癶 (two feet ascending) + 豆 (ritual vessel)
Originally a pictograph showing two feet (癶) climbing up to present a ritual vessel (豆) on a raised platform. The core meaning was 'to ascend' or 'mount,' as when stepping up to make an offering. From this it broadened to 'rise, climb, record, publish.'