Just saw this, look interesting.
Delays over 3 HRS
"If a flight or cancellation is within their control (and not required for safety purposes), and rebooking does not meet a passenger's travel needs (e.g., there is no longer any purpose to the travel), the passenger will be entitled to a refund of their ticket, as well as compensation for inconvenience: $400 for large airlines and $125 for small airlines."
Not sure if this is final rules.