After years of handing out pretzels to passengers, Northwest Airlines is going back to peanuts.

While the return to peanuts will likely be nostalgic for some travelers, families of children with peanut allergies are upset, to the point of canceling a trip on Northwest and vowing to fly only on airlines that don’t serve peanuts.

Margaret Gildner of St. Louis Park, Minn., whose 1-year-old son and 7-year-old niece are allergic to peanuts, said she and others are disheartened by the Feb. 1 policy change.

“There’s no more flights on Northwest for us or any of our family members,” said Gildner, who in November booked a March trip to Florida on Northwest. With the peanut change, she’s cancelled that flight and rebooked on Sun Country Airlines, which doesn’t serve peanuts.

The change comes four months after Northwest was acquired by Delta Air Lines, which is based in Georgia, where peanuts are a huge cash crop. And Delta isn’t shy about admitting support for home-state farmers is one reason for the change.

“Delta is an Atlanta company, and Georgia is an important producer of peanut products, therefore their policy supports their home state,” the company said in a letter to Gildner’s mom, Betsy Parish of Wayzata, Minn. Parish wrote to Delta last week to complain about the change.

Delta spokesman Anthony Black said the change is one of several being made as Northwest and Delta “harmonize” in the wake of the acquisition.

Delta has served peanuts on board its planes for years, he said, and handed out 60 million packages of them last year alone. “It’s a popular item that we have had on our planes for a long time,” he said.

“Through the process of merging the airlines, Delta’s snacks are the snacks that will be carried on board Northwest flights,” he said. Other snacks, cheese crackers and a biscotti cookie also are available, he said.

Peanuts were a staple snack for air travelers until 1998 when the Department of Transportation recommended that large air carriers create a buffer zone around passengers with the peanut allergies. Many airlines decided to go completely peanut-free and switch to an alternate.

Among the airlines that don’t provide packaged peanuts are Air Canada, Air Tran, American, Continental, Jet Blue, Midwest, Sun Country, United and US Airways. If alerted that someone with a peanut allergy is on board, Southwest will not serve peanuts on that flight.

Peanut allergies are the most common life-threatening food allergy in children.