MINNEAPOLIS » Fliers can stop sharpening their elbows. Overhead bins are getting bigger.

Packed planes and a high volume of carry-ons are forcing airlines to expand the space above passenger’s heads. United and Delta are the latest airlines to replace or upgrade bins so they hold more luggage. Engineers at Boeing are designing jet interiors with today’s bulkier luggage in mind.

It’s a chance to placate passengers who feel like they’re thrown into a roller derby every time they board a plane. Because of fees on checked bags, more passengers are bringing carry-ons, which are growing in size. With planes more crowded than ever, bins fill up before everyone has reached their seat. Travelers fight physics and one another to shove one more bag overhead. Or they’re forced to check luggage at the gate.

The result is upset travelers, harried flight attendants and delays.

The percentage of passengers bringing bags on board has hovered around 87 percent in recent years, United Continental says. And "the size of the carry-on has increased. … They are stretching the limits of their bags," says Scott O’Leary, managing director of customer solutions at United Continental Holdings Inc.

Expanding bins is a smart way for airlines to set themselves apart, says Henry Harteveldt, who leads airline and travel analysis at Atmosphere Research Group, a market research firm. "Especially if they cater to the business traveler, they’re hoping it will give them a small but noticeable competitive advantage."

Business travelers, for example, avoid an airline that doesn’t have room for their carry-ons.

At first blush, it might seem like airlines risk giving away fees if more people can fit carry-ons on board. But they’re not risking much, as it turns out.

Airlines often waive bag fees when luggage can’t fit overhead and must be checked at the gate. Business travelers, who generate most of the industry’s revenue, are often exempt from baggage fees anyway.

But will bigger bins encourage fliers to bring larger bags? Airlines hope not, and are trying to crack down before luggage makes it into the cabin.

Airlines expanding their bins include:

» United: The airline is replacing bin doors on 152 planes starting in April. The renovated bins will be on all of United’s Airbus A320s.

» American Airlines: The airline’s new 737s will hold 48 more bags than the planes they are replacing, although they have 24 more seats, too.

» Delta Air Lines: Passengers on international routes like Atlanta-Paris or Minneapolis-Amsterdam are starting to see new bins on the airline’s 767 jets. The compartments hold 26 more bags than the bins they are replacing.

» US Airways Group Inc.: In 2008, it enlarged bins on its 757s, a mid-sized plane flown on routes including Phoenix to Hawaii and Charlotte, N.C., to Dublin. Like United, the change allowed fliers to slide bags in wheels-first instead of sideways.