British Airways Fare Sale to London, Including Bonus Three-Day London Pass -- NY-London $312 Roundtrip; From Philadelphia $336

British Airways has a three-day sale for flights to London -- prices from New York are cut to as low as $156 each way, with flights from Philadelphia to London cut to $168 each way. On top of the fare, there's a Bonus Free 3-day London Pass, which is worth $89 and gets you entrance to over 50 London attractions.

The lowest fares are valid for travel through May 24. Other discounted fares still with the Bonus London Pass are also available for travel through September. The special offer and fare prices are valid through Thursday, April 23rd

Plus, if you register Travelers who register and book online with British Airways you can also receive an additional $20 off per roundtrip (registering is easy at the top right of their website). These fares don't include airport and security fees and taxes.

To get the 3-Day pass as a bonus, you must add it at the same time you book your flight, so pay attention when booking.

To check for dates and flights through British Airways, click this link.