When all iPhones are completed in assembling process and packaged, they will wait to be shipped to the US Apple warehouse, located in Elk Grove, California, and some other distribution centers located around the world, including China, the Czech Republic, Japan, Singapore and the U.K.
iPhone USA transportation route:
When iPhones are shipped to the warehouse and other distributions center, Apple normally choose air freight service provided by Fedex or UPS for shorter period and lower cost. (Forbes)
However, the emission from airplanes and gas released from airports do damage to the environment.
As a public company, Apple apply environment protection to realize its responsibility. The strategy Apple use is to make their product thinner and lighter and make product packages smaller. Such as action enable 60% more iPhone 5s boxes to shipped one time. Fewer transportation flights mean fewer emissions.(Apple)
