How does the relationship between a network and affiliates work?

[akwapez]

My local ABC affiliate is preempting 'Lost" tonight to show the Billy Graham Crusade. Yes, that's right religious programming instead of one of the most popular shows on television. I have emailed both ABC and the local station.

[KurtNYC]

1. Used to work for a network

and it can be somewhat flexible. Affiliates program most of the day with syndicated fare: Maury, Oprah, etc. They do their own local news. Generally they must air the networks' nightly news, primetime programming and the 7am-9am morning show.

But there can be flexibility. Some of the ads during primetime are national and some are local. It much easier for an affiliate to get out of a network prime time show if they have a lot of local advertisers to cover them. Something like the Graham Crusade could replace all of the ad revenue. In other words, the affiliate would sell the whole block of time to the Graham Crusade and then use part of that money to pay the network for pre-sold national ads which won't run because of the crusade.

I hope that makes at least a little sense - it is a strange business.