For the past eight months, sale airfares to the Hawaiian Islands have been far and few between. So when a sale does pops up, as is the case today (4/12), it's big news.

United Airlines is offering deep discounts to two of the most popular of the islands -- Maui and Kauai. And the deals are valid on trips finished on or before March 8, 2012 -- and without any blackout dates.

Round-trip rates to Maui, inclusive of all taxes, surcharges and fees is $591.85 and $651.84 to Kauai.

You can start your trip as soon as tomorrow (no advance purchase required). Sale rates are valid Mondays-Thursdays only. Regularly published rates apply on other days (airfares start from $900). Travelers are permitted to stay up to 60 days, or finish travel by March 12, 2012, whichever date comes first.

United serves both island destinations via Phoenix. Stopovers are not permitted.

This sale has no ticket-by date which means it is expected to vanish in hours. Act fast!

Sale airfares are always subject to change. Every seat on every flight is not offered at the lowest rate. Since only a limited supply of seats is available, act quickly to make your purchase. I recommend starting the search for available seats at Kayak.com vs. calling an airline directly. You can also search for the sale at travel Web sites such as Expedia or Travelocity, etc. Airlines can discontinue or pull a sale price without notice when the offer is deemed "sold out," or when that rate does not have a "ticket-by" date.

Clara Bosonetto is a retired travel consultant.