THE Syfy Channel celebrates America's birthday with a 20-hour July 4th marathon of the cult classic The Greatest American Hero, which hasn't been seen on national television since its original network run in 1983. The holiday celebration airs Sunday, July 4th from 9:00 a.m. - 5:00 p.m. EST/PST. Featuring a most unlikely superhero, The Greatest American Hero aired from 1981-83 and stars William Katt, Robert Culp and Connie Selleca. Katt portrays Ralph Hinkley, a young high school teacher in Los Angeles who is set upon by extraterrestrials while on a field trip in the desert. The aliens give him an incredible red flying suit with unknown powers - unfortunately, Ralph loses the instruction book. Culp plays a neurotic FBI agent who persuades Ralph to use his new powers to fight crime. Selleca is Ralph's girlfriend, an attorney.