I noticed that in Airport, Airport 75 and Airport 77 as well as other movies made in the 70's such as Towering Inferno for example: There is a significant age difference between the leading men and their female partners where the men are always 15 to twenty years older. I assume it was a sign of the times, I really don't know. For example in Airport Burt Lancaster is paired with Jean Seberg and Dean Martin with Jackie Bisset, In airport '75 Charlton Heston with Karen Black and Airport 77 Jack Lemmon with Brenda Vaccaro. In TI Paul Neuman is with Faye Dunaway, again much older guy. I wonder if that is so in other 70's movies or just disaster ones.
15-20 years older is being conservative. It was a sign of the times for decades in Hollywood, still is occasionally. There are countless examples in film history of the male partner old enough to be the female partner's father- or grandfather. Male stars like Gable, Stewart, Bogart, Astaire, Grant were matched up with far younger women from Marilyn Monroe to Audrey Hepburn to Grace Kelly. Leading men stars were allowed to keep that status WAY past the age star leading women usually began losing roles to the next sweet young thang.
It is something that i have wondered about as well,another couple of examples are Charlton Heston and his girlfriend Geneviève Bujold in Earthquake (20 years)Ernest Borgnine and his wife Stella Stevens in The Poseidon Adventure (30 years)
You know a big reason there had been so many aging (mostly male) stars still headlining movies up into the 1970s was the movie attendance demographics were still largely consisting of adult rather than teen and younger ticket buyers. The great shift to a true youth culture at the movies began as early as the late 60s and came into force in the 70s with all the big blockbusters like Jaws, Close Encounters, Star Wars etc. Also of course the advent of all those boob, penis, vagina, and poop-joke teen romps, as well as the slasher films. Anyway, that "older" and "family-oriented" movie audience of all those preceding decades grew up with stars like Heston, Wayne et al so the studios kept feeding the masses the same actors even as they aged (not so well for some). When the male stars started out they were fairly comparable in age to their female leads but that gradually changed to quite ridiculous age gaps as aging actresses were replaced by younger starlets.
You are right, turtletommy, the audience changed dramatically in the 70's. Last night I had the unfortunate experience of having to watch a 70 year old Clint Eastwood trying to make boogie with a 23 year old lass in "True Crimes". Clint didn't look his age .... he actually looked to be about 127, which made it even worse! And this movie came out only 11 years ago.
"The internet is for lonely people. People should live." Charlton Heston
And there was Fred Astaire in The Towering Inferno. He was 20 years older than Jennifer Jones. This kind of casting happened way before the 70s. In 1957, Astaire was paired with Audrey Hepburn in the musical Funny Face. The age gap was 30 years.
In the 1961 comedy The Pleasure of His Company, Astaire's ex wife in the movie was played by Lili Palmer, who was 15 years younger. Palmer's second husband in the film, however, was played by Gary Merrill, who was a year younger than her.