The other day, I was about to head out on the trails for my annual attempt at completing a couch-to-5K program, when I realized that my iPhone battery was almost out of juice. I didn't want to risk having my phone die while I was out on the relatively deserted trails (what if I got attacked by angry squirrels and needed to call for help?) And I needed to leave the house soon or I wouldn't be able to complete the workout before sunset.
Fortunately, there is a way to charge your iPhone more quickly: Just swipe up from the bottom of your homescreen to bring up Control Center and turn on Airplane Mode before you plug your phone in. With your iPhone's wireless radios and GPS turned off, the battery will charge faster.
In Airplane Mode I was able to charge my battery enough to get me through my workout with power to spare, and quickly enough that I was out of the woods before the sun went down.