It seems that the veteran actor of stage and screen, Gerard Sanders, will be playing Tony Stark's father in Jon Favreau's Iron Man. Comics2Film found this news in the program for A Night of Vignettes directed by Sal Landi which is now running in London.
Within the program, Sanders' description reads:
Gerard Sanders can be seen in Paramount Pictures Iron Man as Robert Downey Jr.'s father, to be released May 2008.
CLICK HERE to see the program.
Iron Man, starring Robert Downey Jr., Terrence Howard, Jeff Bridges and Gwynth Paltrow flies into theatres on May 2, 2008.