Airlines continue shrinking passenger space to increase profits, while U.S. fliers are getting bigger, as is evident by rising obesity rates.

One of the world's largest aircraft makers, Boeing Co., just announced several upgrades to its long-range 777 jet, including changes that will allow airlines to squeeze in 14 extra seats and narrow the lavatory by 8 inches.

Hawaiian Airlines became the latest carrier to install new "slim line" seats in 18 of its Boeing jets, allowing an extra row of five seats per plane.

A new survey found that most fliers are willing to pay more for roomier seats, but not much more: 59 percent said they'd pay up to $20 extra; 9 percent would pay more than $20.