Lost Season 6 Episode 16 (Lost s06e16 ) with title “What They Died For” airs on Tuesday, May 18th 2010 at 09:00 pm via ABC.
Here is summary for Lost Season 6 Episode 16 :

Locke devises a new strategy. Elsewhere, Jack’s group searches for Desmond. While Jack’s group searches for Desmond, Locke comes up with a new plan. Ana Lucia Starring by Michelle Rodriguez. Rousseau Starring by Mira Furlan.

Few hours after original series aired on TV, online streaming video for Lost Season 6 Episode 16 usually available on Net and of course, if video available, as soon as possible will show you where you can watch this episode for free.