Anyone that has taken a plane knows that there's almost always a war for room in the carry-on bins.

With airlines increasingly asking a fee for checked-in baggage, but also for the seemingly ever-expanding wardrobe people seem to take on-board (get over yourselves, people!), overhead bins space is stretched to the maximum (it's actually the only reason I try to get in first in the plane).

Space. That's also the name that Boeing is giving to its newer solution, the Space Bins. 

More space. More carry-ons. An image speaks better than words:

Stacked. (image credit: Boeing)

Stacked. (image credit: Boeing)

Alaska Air will be the first airline to receive the new bins on their new 737s next year. They allow to stack the standard (if there's such thing as standard!) carry-on vertically

[They] will hold as many as 174 standard carry-on bags, a 48 percent increase compared to current bins that hold up to 117 bags. Space Bins are deep enough to store nonstandard items, such as a guitar.

The hope is obviously that it improves boarding performance and require less intervention from the crew.

Boeing says airlines will be able to retrofit current 737 models with those.

Although not exactly the same, the Dreamliner has what Boeing touts the "industry's largest baggage bins". Here's a picture:

A domino effect. (image credit: Boeing)

A domino effect. (image credit: Boeing)

Years of traveling have shown me that different airlines adopt different policies. On long-haul, due to the size of the aircrafts (the 777 bins are ginormous!), it's usually not an issue at all.

On short-haul, it's another story. Some companies are very lax—but end up having to require last-minute checking-in when the aircraft is full. Some are very strict (especially low-cost carriers) but end up displeasing the passengers much for what sometimes is just an inch above the limit.

I even remember seeing an airport that had placed plexiglas on the X-Ray belt, shaped to the size of the standard (again, that varying standard!) carry-on: your luggage didn't go through? Back to the check-in counter.
I admittedly liked the idea.

Since you don't always know what you're actually going to get, the expansion of the overhead bins is welcomed.

As long as airlines do not increase their carry-on limits, that is.