A short Wikipedia biography is here and a fairly brief biography on the Norman Rockwell Museum site is here. A more detailed biography can be found here. Commentary on his methods is here. Some statements by Briggs himself are here and here. David Apatoff writes about Briggs' sketchbooks here.
Briggs was a top-notch illustrator. I hope a book about him and his art is in the works somewhere.
Briggs drew the daily Flash Gordon comic strip and later took over the traditional Sunday version from its creator, Alex Raymond. Raymond was the best at drawing it, but Briggs was not far behind.
This was an odd advertising campaign for a low-priced car because a Plymouth does not appear. Some luxury can brands had used this strategy, however, apparently somewhat successfully.
I'm not sure if this is for Buick or American Airlines. And it might not be for an advertisement. I am clueless regarding this.
Briggs illustrated for American Airlines and General Motors. The DC-6 in the background is positioned similarly to such planes in a series of American Airlines ads, but it lacks the complete AA paint scheme. The Buick is clearly a Buick, not the sort of anonymous car design illustrators placed in settings unrelated to a specific automobile brand. The Buick also seems to have a New York license plate, something unusual in car ad illustrations.
From the days when smoking was allowed on flights.