One of the the privileges of parenthood – at least for parents of young kids – is getting to be one of the first to board airplanes.

But soon kids and their car seats will have to wait in line, at least if they fly Southwest.

The airline said Wednesday that it’s tweaking its “open seating” policy, assigning boarding numbers – but not assigned seats – to passengers. It also plans to eliminate the practice of letting families board first.

Starting Oct. 2, families who don’t hold the coveted “A” boarding passes will have to wait until passengers in that group have been seated – that’s the first 60 seats.

“I see a lot of tantrums in our traveling future,” said Stephen Stewart, an advertising creative director from Berkeley and father of a 22-month-old daughter.

In a Dallas news conference Wednesday, chief executive Gary Kelly said the policy was changed so that late-arriving families couldn’t jump ahead of others who had waited in line to board.

But it may not sit well with parents bringing carriers, strollers and squirmy toddlers into the cabin.

“In my case, I don’t see it being much of a problem,” said Charlotte Ross of San Carlos and a mother of three. “But some people like to get situated with their stuff and not have to deal with the masses. For sure, it’s a bummer.”

Southwest had considered dropping its 36-year policy of open seating and switching to an assigned-seating system used by other airlines. But after surveying customers, it found that only about 30 percent wanted a change.

“Customers like choosing their seats. They don’t like standing in line,” Kelly said. “Our goal is to give customers back what they value most, which is time.”

Kelly said that assigned seating actually lengthened the boarding process by up to four minutes.

Southwest will keep its system of boarding in three groups, but starting in November, numbers will be assigned to each passenger within a group. Fliers will then board according to their group and number – A-1 will board first, A-2 second, and so on. Once on board, they can sit wherever they choose.

Southwest tested reserved seating last fall on a number of flights from San Diego and again last month in San Antonio. Surveys indicated that customers preferred the airline’s traditional system.

Beth Harpin, a spokeswoman for Southwest, said the airline also tested the new family boarding policy in San Antonio and found it largely successful. She said that seniors and people with physical disabilities will still be allowed to pre-board.

“The most unfavorable remarks have been related to not knowing that the process had changed,” she said. “What we’re finding is that, once on board, families realize that they’re still able to sit together. “Over time, we think people will get more comfortable with it.”

But some parents clearly don’t believe that.

“It’s going to have a pretty big impact on us because we travel with so much stuff,” said Stewart. “The idea of doing it in queue with everybody else and having six bags and a stroller, we’re going to inconvenience a lot of people.

“For being a budget airline, I always thought Southwest had good customer service. This feels like the opposite of that. It makes them seem less family-friendly.”

But Shai Dallal, an art director from Menlo Park, said he and his wife welcome the chance to board later with their two children, ages 3 1/2 and 21 months.

“With kids, it doesn’t matter if the flight is on time or late, or whether you board first or last,” he said. “The clock is ticking to get them entertained, and they don’t care about the circumstances. Our preference is to be on the plane as little as possible.

“I feel bad that they’re restricting it, but we prefer to have them running in the terminal until the last moment possible.”

Southwest, which operates 3,300 flights a day and carried more than 96 million domestic fliers last year, isn’t likely to feel a financial pinch from these changes. It still is favored by fliers who prefer low prices.

“I can’t say I’m going to avoid the airline, no,” said Ross. “If it’s a cheap fare, I’m going with it.”