Learn Hardcore Indonesian: Jangan lupa pasang sabuk pengaman ketika pesawat lepas landas. - Don’t forget to fasten your seat belt when the plane takes off.

Jangan alone means “don’t,” but needs a verb or adjective to complete the thought.
Lupa means “forget.” Combined, jangan lupa literally means “don’t forget,” and is a common way to say “please remember to…” in Indonesian.
It’s an imperative phrase that both forbids forgetting and reminds the listener of the next action.

Why is the verb pasang used instead of memasang?

Pasang is the root (bare) form of the verb “to install/fasten.”
Indonesian imperatives often use the root form for brevity and directness: Pasang sabuk pengaman!
Memasang is the meN-form (active transitive) and is also grammatically correct: Jangan lupa memasang sabuk pengaman…
Using the root (pasang) simply makes the instruction shorter and more conversational.

What’s the difference between pasang sabuk pengaman and pakai sabuk pengaman?

Pasang = “to fasten/secure” (you attach the belt).
Pakai = “to wear/use” (you put something on).
On a plane, we want you to fasten your seat belt so it won’t come loose, hence pasang.
Pakai sabuk pengaman would mean “wear the seat belt,” which is also understood but less precise for the action of clicking it in.

Why is sabuk pengaman used instead of sabuk keselamatan or tali pinggang pengaman?

Sabuk = “belt.”
Pengaman is a noun derived from aman (“safe”), so sabuk pengaman = “safety belt.”
Sabuk keselamatan (“safety belt”) is equally correct but slightly less common in everyday speech.
Tali pinggang also means “belt,” but sabuk is the standard term for seat belts in transportation contexts.

What does ketika mean, and can it be replaced with saat or waktu?

Ketika means “when.”
Saat also means “when” and is fully interchangeable here: saat pesawat lepas landas.
Waktu is a noun meaning “time,” but you can say waktu pesawat lepas landas in casual speech.
Ketika and saat are slightly more formal; waktu is more conversational.

What is the literal meaning of lepas landas, and why is it two words?

Lepas = “loose, release.”
Landas = “ground, runway.”
Together lepas landas literally describe “release (from) the runway,” i.e., “take off.”
Many aviation terms in Indonesian are compound verbs formed by combining two roots for clarity.

There’s no subject in the sentence—who are we talking to?

In Indonesian imperatives, subjects are often omitted.
The understood subject is “you” (plural or singular, depending on context).
Jangan lupa pasang sabuk pengaman… simply tells the listener(s) “Don’t forget to fasten (your) seat belt when the plane takes off.”