In 1968 United had First Class (F), Coach (Y) and Jet Economy Coach (K) fares on the larger A/C they flew at the time (DC-8s and B-720s). The F and Y fares included meals, K class did not include meals. The K fares were then priced about 10% below Y. Having 2 classes of coach travel might be the way to go about it again which would allow passengers a choice between a full service coach with meals and a lower cost option without meals. Also, the F & Y fares during that time included advance seat assignment and the K fare did not.
The other lower cost fare option which was available at that time on most airlines was the FN or YN fares. Those were fares below the regular F and Y fares on certain routes for flights departing after 9 PM.