Can an engine run on air? I think it can, but I am not sure

Unfortunately, air alone can't be used as a fuel.

First, energy has to be stored in it by squeezing the air tightly using a mechanical air compressor.

Once the compressed air is released, it expands. This expanding air can be used, for example, to drive the pistons that power an engine.

Hello,

NO, and engine can run on steam, gas and other things but not air.

-Bella