"Poslední vlak už odjel."

Translation: The last train has already left.

[walkinwolk]

We don’t always add “has” in a sentence like this unless you want to sound formal. “The last train already left” should be OK.

[VladaFu]

That seems to be true. There are enough occurrences to accept this, although ngrams shows preference for present perfect.

[CathyBowde1]

It depends where you come from, walkinwolk, in the UK "has already" left would be standard. No formality about it.