[Arky]

To add to the post above..... from the506:

Flex Scheduling

•Between weeks 11 and 16, the scheduled (or "pencilled-in") NBC Sunday Night game may be replaced with a "flex" game, depending on competitiveness or ratings concerns. It is the NFL and not NBC that makes the decision to flex a game. The decision is made at least 12 days in advance, and the limits on national broadcasts described above are still in effect. The NFL may also simply decide to make the originally scheduled game official. (Note: in 2011, as Christmas falls on a Sunday and most games are on Christmas Eve instead, flex scheduling does not apply to week 16.)

•In week 17, the NBC game is determined only one week in advance (and usually first announced during the week 16 Sunday Night game), and no game is pencilled in on the original schedule.

•CBS and FOX can each protect five games between weeks 11 and 16 from being flexed to Sunday night. Their decisions are made after week 6. They cannot protect any week 17 games.

•CBS and FOX games may also switch timeslots with 12 days notice (or 6 in week 17) for ratings concerns. These may or may not be called a "flex" depending on who you talk to.