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.
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"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.
Last week, American also brought back complimentary economy cabin snacks, and began serving Biscoff cookies and pretzels in the main cabin on its transcontinental routes (between New York's JFK and Los Angeles or San Francisco, and between Miami and LAX). The carrier said that it would begin offering an assortment of complimentary snacks in the main cabin of all domestic flights by April 1. American dropped its free economy class snack service in 2003, while merger partner US Airways, did the same in 2008.
Travel watchers say the environment has changed from several years ago, when airlines were trying hard to cut costs.
"If you look at the state the industry was in at the time, airlines were looking for survivability. We're now at a point where we're investing in the customer experience," said Fern Fernandez, American's vice president, global marketing.
Industry watchers say a few other factors are at play — namely cheaper oil.
"United is financially able to add snacks back thanks to low fuel prices, and doing so helps cement the narrative that they've turned the corner for their customers," said Gary Leff, a travel specialist at View from the Wing.
American decided to offer complimentary snacks "since their major competitors do," he said. "It has the added benefit of differentiating their product from ultra-low cost carriers, like Spirit, with whom they increasingly have to compete."
Additionally, starting in May 2016 American Airlines will bring back something else economy class passengers have been missing: complimentary meal service — but only on flights between Hawaii and Dallas/Fort Worth International Airport.
American and United are generating buzz for bringing back complimentary main cabin snack service, but other domestic airlines have been offering it all along.
"Delta has been providing customers with consistent snacking options since the 1940s," Delta spokeswoman Catherine Sirna told CNBC. The airline now serves more than 235 million packages of peanuts, pretzels or Biscoff cookies, combined, each year.
A spokeswoman for Southwest, which has always provided complimentary snacks to its passengers, said the carrier doled out more than 106 million bags of peanuts and more than 45 million bags of pretzels last year. On certain flights, Southwest offers a broader choice of snacks like cookies and crackers.
Seattle-based Alaska Airlines offers main cabin passengers complimentary snack mixes, and its regional carrier Horizon Air also offers complimentary tastes of beer or wine made in California, Alaska and the Pacific Northwest.
On JetBlue, passengers are offered unlimited servings from a snack basket that currently includes Doritos tortilla chips, Keebler Elf Grahams, PopCorners popcorn chips and the airline's now-signature Terra Blues potato chips. In 2015, the carrier gave out about 9 million bags of potato chips and 8 million bags of chocolate chip cookies.
A full meal on a flight, however, is still a dicey proposition, and most airlines don't give them out on domestic flights, or trips under a few hours. Yet Hawaiian Airlines remains the only domestic carrier to serve a complimentary, full-tray meal to all guests on its North America routes.
As part of its beverage service, the airline also offers economy passengers a complimentary glass of red or white wine, and a complimentary Koloa Rum Punch.
So can the return of palm-sized bags of pretzels and a couple of cookies be enough to cease frequent complaints from economy class airline passengers, who frequently are up in arms about pricey flights, poor service and cramped seats? Some have their doubts.
Travel experts like George Hobica of Airfarewatchdog.com call the return of free main cabin snack service "window dressing to assuage consumer resentment" over why lower oil price haven't yet been reflected in air fares.
Yet at least one observer thinks even a free cookie can make a difference in the passenger experience.
"Small touches ... are beloved by passengers, and it's not uncommon to see someone praise Delta for the simple but tasty treat on Twitter," said Mary Kirby of Runway Girl Network.
"In fact, one could make the argument that today's mobile, social and very vocal passengers are what's helping drive incremental improvements in the passenger experience on board," she added.
— Harriet Baskas is the author of seven books, including "Hidden Treasures: What Museums Can't or Won't Show You," and the Stuck at the Airport blog. Follow her on Twitter at @hbaskas. Follow Road Warrior at @CNBCtravel.