Jason Reitman (right) is the son of Ghostbusters director Ivan
Iraq war drama The Hurt Locker and recession romance Up in the Air won top honours at the Writers Guild of America awards in Los Angeles this weekend.
Journalist Mark Boal won best original screenplay for The Hurt Locker ahead of winning the same award at the Baftas.
Writer-director Jason Reitman and co-writer Sheldon Turner won the adapted screenplay prize for Up in the Air before going on to win again in London.
Mad Men and 30 Rock were named best TV drama and comedy series respectively.
The Writers Guild awards are the last major Hollywood awards ahead of the Oscars, held this year on 7 March.
Both The Hurt Locker and Up in the Air are up for screenplay awards at this year's event.
David received a lifetime achievement award at Saturday's event
Also recognised on Saturday was The Cove, a film about the slaughter of dolphins in Japan that won the best documentary screenwriting award.
Writer-director Barry Levinson, of Diner and Rain Man fame, received a lifetime achievement accolade at the event.
So did Larry David, the acclaimed writer and performer behind the TV comedies Seinfeld and Curb Your Enthusiasm.
Reitman, who did not attend the Baftas, thanked his father Ivan, best known as the director of Ghostbusters, as he picked up his award.
Boal, meanwhile, acknowledged the troops in Iraq with whom he had been embedded as a journalist before he wrote his screenplay about bomb disposal experts stationed in the war-torn country.