American and British Airways has round-trip flights from Austin (AUS) to London (LHR) for $484, NONSTOP. Flights in May, August, and September. 7-day minimum stay required. Flight may operate as a Finnair/American code-share.
Note: Personal item and carry-on bag are allowed free of charge, but a checked bag will cost +$60 each-way. Upgrades into “Regular Economy” are available for +$45 each-way.
Note: This deal was $444 last November.
Note: Flights on Norwegian may also be available for a slightly cheaper price, but their fare requires a fee for meals, less carry-on weight (22-lbs vs 50-lbs on BA), and higher fees for seat selection and bags. Furthermore, Norwegian has limited flight availability, and only has 3 flights per week for their route, which means if their flight is canceled or missed, your next flight will be several days later. Avoid Norwegian unless the price is about -$200 less than this.