"Mój bogaty wujek kupuje mały samolot."

Translation: My rich uncle is buying a small airplane.

[Kohvikruus]

Why can't an airplane be little? There is even a company, Little Airplane Productions.

[JerryMcCarthy99]

"Little" has been added sometime in the last three years :-) .

[79Ku1]

Is "small jet" possible?

[Jellei]

Too specific. Sure, it may be the most probable nowadays, but maybe he's buying an old plane from a museum that isn't even supposed to fly ;)

"jet" is "odrzutowiec" (or "samolot odrzutowy")