As part of the strategy to fill seats, airlines have trimmed schedules and fleets and more carefully control sales -- meaning that they tend to be short. This gives the carriers a chance to ensure a certain number of seats will be sold, particularly those that are harder to sell because of time of week or year, without giving away the store.
For this sale, the lowest prices will be available on off-peak days, which in the Continental United States are Monday-Thursday. For those bound for the Caribbean, Bermuda and Mexico, off-peak fares are available Sunday-Wednesdays.
And there are some blackout days. All the fine print is here.
To give you some idea of what kinds of savings the carrier is offering, here are some one-way sample fares from Boston: Aruba $154, Atlanta $99, Baltimore $49, Bermuda $134, Charlotte $109, Chicago (Midway) $114, Dallas/Ft. Worth $109, Denver $149, Detroit $119, Fort Lauderdale $99, Fort Myers $104, Houston (Hobby) $109, Key West $139, Las Vegas $159, Los Angeles (LAX) $159, Miami $104, Minneapolis/St. Paul $109, Nassau $104, New Orleans $110, Orlando $99, Pensacola/Gulf Coast $99, Phoenix $149, Raleigh/Durham $94 San Francisco $159, Sarasota/Bradenton $99, Seattle $159, Tampa $99, and West Palm Beach $99.