If you think the television lineup is already peppered with too many can't-miss shows scheduled at the same time this fall, don't finish programming your TiVo just yet. With the official start of the new TV season under way this week, Fox is openly dangling the possibility of moving "American Idol" to Thursdays.

Wasn't this season already insanely competitive enough? Starting tonight, ABC's gutsy move of "Grey's Anatomy" to 8 p.m. Thursdays will set off a fierce ratings battle with CBS' seventh-season whodunit, "CSI: Crime Scene Investigation," also airing at 8.

But Fox Entertainment President Peter Liguori said he believes that the top three networks could still profit with their respective No. 1 series airing on the same crucial night — maybe even at the same time.

"When you have a number of great shows on the same night, the audience expands," Liguori said last week, openly broaching the possibility of a regular Thursday slot for "Idol" when it returns in January.

Fox isn't ready to commit and may not nail down plans until late December.

Is it all just "Idol" speculation? Maybe. After all, Fox made similar rumblings about moving its singing contest to Thursdays last year and never did it.

But Fox openly mulling a risky move for TV's most-watched program highlights how crazily competitive the network business is becoming, with no firmly entrenched leader among the adults aged 18- to 49-year-old demographic group that advertisers covet (CBS has for years been No. 1 in total viewers, a distinction that means little on Madison Avenue).

By moving "Idol," Fox could conceivably control some of the most lucrative ad time in prime time — and also foil rivals' efforts to dominate that night.

"It's certainly shaping up to a much more competitive season than we've seen in a while," said CBS scheduling chief Kelly Kahl. "Everyone's making aggressive moves."

Starting in the mid-1980s, NBC had a lock on the lucrative target audience for nearly 20 years with fare such as "Cheers," "ER" and "The West Wing" — series with sophisticated writing and characters and plenty of appeal for young-adult viewers who were affluent and well educated. But with the fade-out of "Friends" in 2004, NBC went into a free fall, and Fox swept in with "Idol" and took those trophies, albeit by narrow margins.

This fall, NBC's fortunes are almost certain to perk up with the addition of Sunday NFL football.

"The great games on Sunday provide us with a chance to get back in the game," said NBC scheduling chief Mitch Metcalf. He added, though, that football "is not going to solve every problem; we need our new shows to break out."

Among those contenders: Aaron Sorkin's heavily promoted "Studio 60 on the Sunset Strip," Tina Fey's backstage spoof "30 Rock" and a football-themed youth soap, "Friday Night Lights."

Any substantial improvement for NBC could mean that either ABC or CBS winds up in fourth place in 18 to 49 — an outcome both networks will work hard to avoid.

The closeness of the four-network race, and the lack of an undisputed leader, explains why executives are battling so furiously for Thursday — where some of the most expensive advertising time is bought and sold.

When ABC announced "Grey's" move in May, for example, NBC quickly backed away from a Thursday slot for "Studio 60," which landed on Mondays instead.

More recently, ABC displaced two new Thursday comedies to import its buzz-worthy drama "Ugly Betty" from Fridays to a high-traffic spot opposite CBS' "Survivor."

All the shuffling could wreak havoc with well-established viewing patterns. For example, when NBC decided to hustle "Studio 60" out of the 8 p.m. Thursday slot, it replaced it with "Deal or No Deal," the game show with Howie Mandel that draws a less upscale audience than the network typically attracts. That could end up hurting "ER," the network's 9 p.m. hospital drama entering its 13th season.

"Deal" will give "ER" "a significantly lower lead-in than it's had, probably ever," said ABC Entertainment Executive Vice President Jeff Bader. (NBC's Metcalf defended the move, saying that "Deal" is "a different kind of show than the competition will be offering.")

Rivals agree that Fox probably wants to see how this all shakes out before making a decision on "Idol," which since its inception has consisted of a Tuesday performance show followed by a Wednesday results show.