Most (all?) states have no requirement to carry or present ID to officers - you only have to give your name, and sometimes your address depending on the state. There's no Federal requirement to carry ID.
To operate a motor vehicle you need a driver's licence...but your passengers don't. What about riding the bus? You can get on the local Metro, Bolt bus, or Greyhound w/o an ID.
Hitchhiking doesn't require an ID.
Bicycling doesn't require an ID. Nor does walking.
You don't need a pilot's license to fly an experimental aircraft (but I'm sure there are other requirements for operating from an airport).
Hangliding/parasailing doesn't require an ID.
So...only through a commercial airline (private jets don't require IDs) requires proof of identify.