| Attorney here! (Not providing legal advice, though.) The elements of common law civil fraud are as follows: 1. Somebody intentionally misrepresents a material fact in order to obtain action or forbearance by another person ("I am traveling to ILM from SFO" but in fact is going to IAD); 2. The other person relies upon the misrepresentation (United prices the fare as though the passenger were going to ILM instead of IAD); and 3. The other person suffers injury as a result of the act or forbearance taken in reliance upon the misrepresentation (United gets less fare). Note that profit is not an element of fraud, although here, one could argue that the potential fraudster did profit in terms of the difference in fare. So United has a fair argument that, given the facts at hand, intentionally misrepresenting one's travel plans in order to obtain a better fare probably constitutes fraud. |
Now, there could be something United has inserted in the purchase flow of all multileg tickets which assures that the purchaser makes a representation of intent to use every leg, though I've never seen anything like that when purchasing tickets (and a contract of adhesion that United writes that most purchasers will not read, while it may succeed as a contract, probably won't be seen as such a representation for fraud purposes, AFAICT.)