An annual study ranking airlines based on their healthy in-flight food options put Delta Air Lines in the No. 1 spot.

The report by Hunter College New York City Food Policy Center director Charles Platkin, who is also founder of DietDetective.com, called Delta the leader among major carriers.

Overall calories in Delta's in-flight food options are down from 527 to 480, according to the study. But Delta's complimentary snacks are not all great choices, other than almonds, according to the study.

Delta's in-flight snacks in economy class include almonds, pretzels, KIND oats and honey bars and Biscoff cookies, while first class and Comfort+ passengers get premium snacks.

According to Platkin, Delta's menu focuses on "transparency into ingredient and allergen information" and shows which snack items are non-GMO, vegan, gluten-free, kosher and lacto-ovo vegetarian.

Delta’s snack box is also the only non-GMO snack box among airlines, according to the study.

For some of its in-flight food such as wraps and breakfast bowls, Atlanta-based Delta partners with food company Luvo, which targets healthy eaters.

Overall among airlines, the average number of calories in carriers' food options has increased by 13 percent since last year, according to the study, which also looks at nutrients and other factors.

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Atlanta-based Delta Air Lines, the only remaining U.S. passenger airline to fly the 747, is retiring the plane from its fleet. In 1966, Boeing announced plans to build the 747. In 1969, the Boeing 747-100 made its first flight. The 747's distinctive "hump" could be used as a first-class lounge, extra seating or as cargo space. Atlanta-based Delta Air Lines first operated the 747 in the 1970s. In this Oct. 1970 photo, a Delta crew gets set to take off on a pre-inaugural flight over north Georgia. As far