With the iPad Air being the larger iPad and now this reported 'iPhone Air' being the largest iPhone ever, the 'Air' moniker may now be associated with 'large'.
Kind of weird since it initially was associated with low weight and portability. The MacBook line is also doing the opposite, with the MBA being (on average) smaller than MBPs.
Pretty sure Air refers to weight alone, as in the idiom "lighter than air". Air is quite large.