This week marked a special occasion for economy class airline passengers — the return of free snacks on some domestic carriers.
Both United and American Airlines are winning praise from fliers who believed the small but key amenity had all but disappeared forever, along with pillows, blankets and added legroom. Last week, United Airlines began serving complimentary Dutch-style, caramel-filled waffle-shaped cookies (called a stroopwafel) with the morning drink service on flights within North America and Latin America.
Discount domestic carriers like Southwest Airlines and JetBlue have always offered snacks on their flights. However, on flights departing after 9:45 a.m., a free packaged snack mix is now being offered by both United and American.
Read MoreWeak Loonie fuels Canada tourism
"We know even the smallest details can make a big difference in the travel experience," United spokeswoman Karen May told CNBC. "Our customers were telling us they missed the free snacks and were urging us to bring them back."
United last served free snacks back in 2008, while its merger partner, Continental Airlines, dropped complimentary snack service in 2011 (both airlines had been doling out free pretzels and Biscoff cookies). When it made the cut, Continental cited an estimated yearly cost savings of $2.5 million.
United won't say how much it expects to spend on reconstituting the free snack service, but the Chicago-based carrier estimates that, with 230,468 flights scheduled throughout the year, it'll be boarding about 40 million, 180-calorie stroopwafels each year on its planes.