A new spy show from hit director and producer, J.J. Abrams, is part of NBC's return to traditional scripted programming this fall. (Peter Kramer/Associated Press)NBC will make an aggressive return to scripted dramas and comedies, while Fox is mostly tweaking its existing lineup, as U.S. television networks began unveiling details of their upcoming seasons.

After the spectacular failure of moving Jay Leno to prime time five days a week, NBC has given the green light to a dozen new scripted programs, including a number of high-profile series:

• Outlaw, a legal drama starring Jimmy Smits.
• Chase, an action-packed police procedural from Jerry Bruckheimer.
• Love Bites, an hour-long comedy from former Sex and the City writer-producer Cindy Chupack about two women who are the last singles in their circle of friends.
• Outsourced, a comedy about a Midwesterner transferred to India to run his company's new call centre.
• Undercovers, a J.J. Abrams-created spy drama about two retired, married agents pulled back into the business.
• The Event, a conspiracy thriller about a man searching for answers when his financée disappears.

"This new schedule brings NBC back to basics with its commitment to quality scripted programming," Jeff Gaspin, chair of NBC Universal Television Entertainment, said in a statement.

Returning shows include comedies Chuck, 30 Rock, Community, The Office, Parks & Recreation,weight-loss reality series The Biggest Loser, family drama Parenthood and sketch comedy show Saturday Night Live, which will also be celebrated with a 35th anniversary special.

On Friday, NBC confirmed it's ending the venerable Law & Order after 20 years. On Sunday, it also revealed that former cult favourite Heroes will be cancelled.

The Law & Order franchise will continue, however, with the returning Law & Order: SVU to be joined by a new incarnation, Law & Order: Los Angeles.

Fox tweaks

Where NBC was making large changes, however, Fox was generally maintaining its schedule with some modifications, the network revealed on Monday.

Fox is tweaking the length of American Idol's shows and must also find a replacement for the ratings giant's acerbic outgoing judge Simon Cowell. (Dan Steinberg/Associated Press)American Idol remains TV's ratings behemoth, despite sagging an estimated nine per cent in young viewership this past season. So, in a response to audience requests for more performances, the singing competition's Tuesday broadcast will span 90 minutes, with the subsequent Wednesday results show to drop to 30 minutes.

Also, the search for a replacement for departing judge Simon Cowell, who leaves at the end of the current season, is a top priority, executives said.

The network's other music-filled hit, the high school-set newcomer Glee, will return and has also landed the prime post-Super Bowl timeslot in February.

Terra Nova, an anticipated time-travelling epic by Steven Spielberg, is forthcoming, but has yet to be slotted into the schedule.

Other additions include:

• Running Wilde, a comedy starring Arrested Development's Will Arnett as a playboy trying to woo his former sweetheart, portrayed by Keri Russell.
• Lonestar, a prime-time soap about a Texan oil millionaire living a double life.
• Ride-Along, a Chicago-set police drama.
• Raising Hope, about a pool cleaner suddenly faced with raising an infant.
• Mixed Signals, a relationship comedy revolving around three friends.
• Bob's Burgers, an animated series about a man running a struggling restaurant.

Most of Fox's schedule will return, including House, Bones, Fringe, Human Target, Lie To Me, Cops, So You Think You Can Dance, The Simpsons and Family Guy.

Along with counter-terrorism series 24 and Joss Whedon's Dollhouse, shows to end include Past Life, 'Til Death, Sons of Tucson and The Wanda Sykes Show.

New season announcements are still forthcoming from rival networks ABC and CBS.

With files from The Associated Press