Apple has had a problem with making a fourth model of its flagship phones appeal to consumers for a long time. While the base model sells for its price, the Pro model sells for its features and the Pro Max sells for its size, a fourth model has struggled for years.
There was the iPhone mini, which many users now wish would come back, that sold the least out of the entire lineup. Apple replaced it with the iPhone Plus that we know of today but that has also sold the least out of all the models. So now the company wants to experiment with a new approach which targets the demographic that cares heavily about aesthetics.
As such the iPhone 17 Air is going to be an extremely slim phone by modern standards. It will likely be more expensive than the Plus model that it will be replacing but it will also look quite elegant if leaks are to be believed.

A render of the upcoming iPhone 17 Air. | Image credit — Fpt.
Whether these slim phones are actually as popular as these two manufacturers are hoping remains to be seen. I think that they’ll see a lot more success when both companies adopt newer and denser batteries so that the reduction of space doesn’t affect how long the phones last.