Gaps under windows not sure if intentional?

[housecat]

Hello I have some gaps under the windows in my 1980s house - pictures attached.

Sorry for the silly question but I am not sure if they are intentional for ventilation because they look like they’ve been ‘shaped’ rather than just enlarged cracks as a result of settlement etc.? The gaps go through all way to outside.

Does anyone know if I should fill them or leave them? If I should fill them what is the best way please.

Thanks .

 

[blup]

Can you post a pic of the whole window, and how thick are the walls, it may be the camera angle.

Blup