На борту самолёта указан номер.

Because на is governing борту, not самолёта.

The structure is:

• на борту = on board
• самолёта = of the airplane

So literally, на борту самолёта means on the board/side of the airplane, which in natural English is simply on board the airplane.

A useful pattern to remember is:

• на борту корабля
• на борту самолёта
• на борту судна

In all of these, the second noun is in the genitive because it depends on борт.

Борту is the prepositional singular of борт.

The preposition на often takes the prepositional case when it means location:

• на столе
• на улице
• на борту

So:

• dictionary form: борт
• prepositional singular: на борту

This is part of the fixed expression на борту = on board.

Yes, there is a nuance.

• на борту самолёта = on board the airplane
• в самолёте = in the airplane

Both can sometimes translate similarly, but на борту is the more standard expression for being aboard a vehicle such as a plane or ship. It sounds a bit more official or transport-related.

Compare:

• На борту самолёта есть Wi‑Fi. = There is Wi‑Fi on board the plane.
• Я оставил сумку в самолёте. = I left my bag in the plane.

So на борту often emphasizes being aboard as a passenger or as part of the vehicle environment.

Указан is the short-form passive participle of указать.

It means something like:

• indicated
• specified
• stated
• shown

In this sentence, it works like a predicate:

• номер указан = the number is indicated / the number is specified

This short form is very common in formal written Russian.

Compare:

• указанный номер = the indicated number — full form, used like an adjective
• номер указан = the number is indicated — short form, used as the predicate

Because Russian normally omits the verb to be in the present tense.

So:

• номер указан literally looks like number indicated
• but it means the number is indicated or the number is shown

Russian does use быть in the past and future:

• Номер был указан. = The number was indicated.
• Номер будет указан. = The number will be indicated.

But in the present tense, the linking verb is usually left out.

Because номер is the grammatical subject of the sentence.

The sentence is built like this:

• На борту самолёта = location
• указан = predicate
• номер = subject

So the basic core is:

• номер указан = the number is indicated

Since номер is the thing being described, it stays in the nominative singular.

Also notice agreement:

• номер указан — masculine singular
• цена указана — feminine singular
• число указано — neuter singular
• данные указаны — plural

Both are possible, but the emphasis changes.

• На борту самолёта указан номер.
  This starts with the location, so it sets the scene first: on board the airplane...

• Номер указан на борту самолёта.
  This starts with номер, so it puts more focus on the number itself.

Russian word order is more flexible than English, and word order often reflects topic and emphasis, not just grammar.

So the given sentence sounds a bit more like formal written information where the location is being introduced first.

Yes. Указан comes from the perfective verb указать.

Aspect pair:

• указывать — imperfective
• указать — perfective

With short passive participles like указан, the perfective source often gives a sense of a completed result:

• номер указан = the number has been provided/specified

If you used a present-tense imperfective passive-style construction instead, the meaning would be different in tone:

• номер указывается = the number is being indicated / is indicated as a general rule

So указан sounds more like a finished, established fact.

It sounds fairly formal and a little context-dependent.

The sentence is grammatical, but by itself номер is quite vague. In real usage, Russian often specifies what kind of number it is, for example:

• На борту самолёта указан регистрационный номер.
• На борту самолёта указан номер рейса.

So the original sentence is fine, but it sounds a bit like a formal label, instruction, or description where the listener already knows what номер is being discussed.

The stress is:

• На борту́ самолёта указа́н но́мер.

A few pronunciation notes:

• ё in самолёта is pronounced yo and is always stressed
• борту́ has stress on the last syllable
• указа́н has stress on the last syllable
• но́мер has stress on the first syllable

A rough pronunciation guide:

• na bar-TOO sama-LYO-ta oo-ka-ZAHN NO-mer

Also, in normal writing, ё is sometimes replaced by е, but the pronunciation is still ё when the word is самолёт / самолёта.

Because Russian has no articles.

So номер can mean:

• a number
• the number

The exact meaning depends on context.

In this sentence, English would usually choose the number if the number is already understood from context, but Russian simply uses номер and lets the situation clarify it.