Boeing believes it can add 14 seats to its best-selling twin-engine jetliner by making the changes.

But the bathrooms on a plane are not the only reduction.

A few years ago, a report showed that airline seats have gotten smaller. (Watch video report)

For airlines, the reason is simple: the lighter and smaller models cut costs and widen profits.

Meanwhile, airline profits are expected to reach new heights this year, but that doesn't necessarily mean lower fares for travelers.

The International Air Transport Association said airlines are expected to earn $29.3 billion in net profit this year, which is a record high.

More efficient use of planes and lower fuel costs helped the earnings.

But transportation officials said rising costs of airport charges and taxes will keep fares from going down.