Three U.S. airlines have agreed to each pay hundreds of thousands of dollars in fines to resolve government claims that they violated rules aimed at protecting consumers, CNBC reports. The U.S. Transportation Department said on Friday it fined Frontier Airlines $400,000 for violating oversales and disability rules; American Airlines (Nasdaq: AAL) $250,000 for failing to make timely refunds to passengers; and Delta Air Lines (NYSE: DAL) $200,000 for filing inaccurate baggage reports. Delta failed…