Nike first developed an air cushioning system for their athletic shoes in 1979, but it wasn't until 1987 that the first models with a visible air pocket in the soles became available. The air bubble is formed by a plastic bladder embedded in the midsole of the shoe. The size and shape of the bladder varies by model, but in some Nike Air shoes, it's possible to see right through the soles. Since they're on the lowest part of the shoe, they can become cloudy or dirty.
Clean the surface of the shoe with a damp rag, wiping away any dirt.
Spray the Nike Air shoes with shoe cleaner or a mild detergent mixed with water.
Wet an old toothbrush and use it to scrub the dirt out of the cracks and crevices of the shoe, including around the air bubble.
Wipe the surface of the shoe with a clean damp cloth to remove the dirt. You can rinse them under a faucet first if they are very dirty. Be careful not to get water inside the shoe.
Dry off the shoes with a towel and allow them to finish air drying before wearing.