Prijavljujem nepravilnost aviokompaniji.

Because prijavljujem is the 1st person singular present tense form of the verb prijavljivati.

The ending -em here tells you the subject is I, so Serbian does not need the pronoun ja.

Like many Serbian present-tense forms, prijavljujem can mean either:

• I am reporting
• I report

The exact English translation depends on context.

In Serbian, the subject pronoun is often left out when it is clear from the verb form.

So:

• Prijavljujem = I am reporting / I report

You could say Ja prijavljujem..., but that usually adds emphasis, as if you are stressing I in particular.

Because nepravilnost is the direct object of the verb, so it is in the accusative case.

However, this noun belongs to a group of feminine nouns ending in -ost, and for these nouns, the nominative singular and accusative singular are the same.

So:

• nominative: nepravilnost
• accusative: nepravilnost

That is why the form does not visibly change.

Because aviokompaniji is in the dative singular, which is used here for the recipient, meaning to the airline.

The basic form is:

• aviokompanija = airline

In the dative singular, it becomes:

• aviokompaniji = to the airline

So the sentence structure is basically:

• I report
  • an irregularity
    • to the airline

Because Serbian often expresses meanings like to someone by using the dative case instead of a separate preposition.

In English:

• to the airline

In Serbian:

• aviokompaniji

So the idea of to is built into the noun ending.

This is a question of aspect, which is very important in Serbian.

• prijavljivati / prijavljujem = imperfective
• prijaviti / prijavim = perfective

Very roughly:

• imperfective focuses on the process, repetition, or ongoing action
• perfective focuses on a completed act

So:

• Prijavljujem nepravilnost aviokompaniji suggests I am reporting / I report
• Prijaviću nepravilnost aviokompaniji would mean I will report the irregularity
• Prijavim is not normally used as a plain present meaning I report; with perfective verbs, present forms often refer to future meaning or appear in special contexts

Yes, Serbian word order is fairly flexible because cases show each word’s role.

The neutral order here is:

• Prijavljujem nepravilnost aviokompaniji.

But other orders are possible, for example to shift emphasis:

• Aviokompaniji prijavljujem nepravilnost.
• Nepravilnost prijavljujem aviokompaniji.

These are grammatical, but they sound more marked or emphatic. The original sentence is the most neutral and natural in many contexts.

Aviokompanija is a feminine noun ending in -a.

Its cases in the singular begin like this:

• nominative: aviokompanija
• genitive: aviokompanije
• dative: aviokompaniji
• accusative: aviokompaniju

In this sentence, you need the dative because the airline is the one receiving the report.

No. Depending on context, prijaviti / prijavljivati can have several related meanings, such as:

• to report
• to register
• to sign up
• to notify
• in travel contexts, sometimes to check in

In this sentence, because the object is nepravilnost and the recipient is aviokompaniji, the meaning is clearly to report.

Yes, it is a normal formal word. Nepravilnost often means something like:

• irregularity
• impropriety
• something not done correctly
• a discrepancy

It can sound a bit more formal or official than a general word like problem.

So this sentence sounds appropriate in a complaint, report, or customer-service context.