Ukrcajna propusnica je u ručnoj prtljazi.

Yes. Ukrcajna propusnica is a standard way to say boarding pass.

Literally:

• ukrcajna = boarding / for boarding
• propusnica = pass / permit

So the phrase is quite transparent in Croatian: it is basically a pass for boarding.

You may also hear other travel-related terms in real life, but ukrcajna propusnica is a correct and natural expression.

Because after u meaning in, Croatian usually uses the locative case when talking about location.

The basic form is:

• ručna prtljaga = carry-on luggage / hand luggage

But in this sentence, it means in the carry-on luggage, so the noun phrase changes to locative:

• u ručnoj prtljazi

So:

• ručna prtljaga = nominative, dictionary form
• u ručnoj prtljazi = locative, used after u for location

It is in the nominative case, because it is the subject of the sentence.

Structure:

• Ukrcajna propusnica = the subject
• je = is
• u ručnoj prtljazi = in the carry-on luggage

So this is a very typical Croatian sentence pattern:

• Subject + je + location

The adjectives must agree with the nouns they describe in gender, number, and case.

Here:

• propusnica is feminine singular nominative
• so the adjective is ukrcajna (feminine singular nominative)

And:

• prtljazi is feminine singular locative
• so the adjective is ručnoj (feminine singular locative)

Agreement is very important in Croatian. The adjective changes because the noun changes.

Because Croatian does not have articles like a/an or the.

So:

• Ukrcajna propusnica can mean a boarding pass or the boarding pass
• the exact meaning depends on context

In your sentence, English would naturally say The boarding pass is in the carry-on luggage, but Croatian does not need a separate word for the.

Croatian has a tendency for short unstressed words, called clitics, to appear near the beginning of the sentence, often in second position.

Here:

• Ukrcajna propusnica = first unit
• je = second-position clitic

So:

• Ukrcajna propusnica je u ručnoj prtljazi.

This is the normal and natural order.

You should not usually put je at the end or far later unless the sentence structure requires something special.

Yes, but it means something slightly different.

• u ručnoj prtljazi = in the carry-on luggage / hand luggage
• u ručnoj torbi = in the handbag / hand-carried bag

So prtljaga is more like luggage/baggage, while torba is a bag. They are related ideas, but not the same thing.

Not always. U can take either:

• locative for location: in, inside
• accusative for motion toward somewhere: into

In this sentence:

• u ručnoj prtljazi = in the carry-on luggage
  so it is location, therefore locative

Compare:

• Propusnica je u ručnoj prtljazi. = The pass is in the carry-on luggage.
• Stavljam propusnicu u ručnu prtljagu. = I am putting the pass into the carry-on luggage.

Notice how the form changes:

• u ručnoj prtljazi = locative
• u ručnu prtljagu = accusative

Prtljaga is grammatically singular in Croatian.

So:

• ručna prtljaga is singular
• u ručnoj prtljazi is also singular, just in the locative case

It works somewhat like English luggage or baggage, which are also treated as non-countable in many contexts.

A rough pronunciation guide is:

• Ukrcajna ≈ oo-KRTS-eye-na
• propusnica ≈ pro-POOS-nee-tsa
• je ≈ yeh
• u ≈ oo
• ručnoj ≈ ROOCH-noy
• prtljazi ≈ PRT-lya-zee

A few useful notes:

• j is pronounced like English y
• č is like ch in church
• c is like ts
• lj is a soft sound, similar to ly in million for many learners

Yes, Croatian word order is more flexible than English, but not every version sounds equally natural.

The neutral version is:

• Ukrcajna propusnica je u ručnoj prtljazi.

You could also say:

• U ručnoj prtljazi je ukrcajna propusnica.

That puts more focus on the location, something like:

• In the carry-on luggage is the boarding pass
• or more naturally in English: The boarding pass is in the carry-on luggage

So the meaning stays basically the same, but the emphasis changes.

Yes. In most contexts, ručna prtljaga corresponds to:

• hand luggage in British English
• carry-on luggage or carry-on baggage in American English

So if you already know one of those English terms, that is the right idea.

You negate je by using nije:

• Ukrcajna propusnica nije u ručnoj prtljazi.
• The boarding pass is not in the carry-on luggage.

This is the standard negation pattern for to be in the third-person singular:

• je = is
• nije = is not