Learn Arabic (Modern Standard): كانت أول رحلة طيران في عام ألف وتسعمئة وثلاثة. - The first aviation flight was in the year nineteen hundred and three.

Unlike English, where we usually split years into chunks like "nineteen" and "oh three", Arabic reads the full number out loud. You literally say "one thousand and nine hundred and three" (ألف وتسعمئة وثلاثة). Notice that we use و (and) between every single part of the compound number.

How is the word for "nine hundred" (تسعمئة) formed?

It is a combination of تسع (nine) and مئة (hundred). In Arabic, the hundreds from 300 to 900 are written and pronounced as a single combined word, unlike English where they stay separate.

Why does the number three (ثلاثة) have a feminine ending if the word for year (عام) is masculine?

This is a great reminder of the "reverse gender" rule for numbers 3 through 10. Since the counted noun عام (year) is masculine, the number takes the feminine form ثلاثة (with a Ta' Marbuta). Even though the noun and the number three are separated by "one thousand and nine hundred", the rule still applies to the final digit!

Why is the verb كانت (was) in the feminine form?

The verb needs to agree with the main subject of the sentence. Here, the subject is "the first flight" (أول رحلة). Because the core noun رحلة (flight or trip) is feminine, the verb must be the feminine كانت rather than the masculine كان.