Airlines should let passengers reserve overhead bin space. Today, the overhead bin is hotly competed for. People want to board first to make sure they get it. If you don't, they gate-check your bag, adding delays, lack of access to your stuff, and risk of damage -- I had some very important equipment damaged that way once and never let them gate check that sort of thing any more.

In addition, most people put their "personal item" up there too -- I will admit to doing this myself -- rather than under the seat. This uses up more space and pushes some people into gate check. Often you find space, but nowhere near your seat, and there's a crazy squeeze to get things at the end. As airlines started charging more for checked luggage, people started bringing more carry-ons, slowing down security. Airlines have started charging for carry-ons now, including creating special fares that don't allow a carry-on bag.

How would reservation work?

To reserve space, you would have to provide true dimensions for any carry-on you wish to put up there. You would get allocated a space as close to your seat as possible.

The airline would put a coloured addressable LED strip along the luggage bins, as well as small panels able to display numbers or seat numbers. You would put your bag in the marked slot. If it didn't fit because you measured it wrong, it would be gate-check for you, or movement to another part of the plane on light flights.

You would get your reservation when checking in. (You might not know what bag you will use when buying the ticket.) You could also order it beforehand, but the allocation would not get calculated until boarding. Elite passengers and higher fares would get first dibs, including in their fare. Others might have to pay for the space, possibly by the inch. There could even be an auction (Dutch style.)

You could also specify the size of your personal item. If there's room, space could be allocated for it. Otherwise it goes under the seat.

You could also specify strangely shaped items like long tubes or sports equipment. An algorithm could find a place to fit them and communicate it. You would need to have a mobile app for these, perhaps.

Once everybody has a mobile app, this becomes a bit easier to implement. You don't need a digital display. You just need a ruler with numbers along the bins. You would then get told, "Your bag goes from marker 230 to 242." This is much cheaper, but it is harder to reconfigure it just before boarding (or even after boarding when things don't fit) the way it is with a digital display.

This system could also be done as a hybrid. It could be that reserved space would only be for first class, elite, or high paying passengers. Others would still compete and pack as they can in the unallocated space, which would be most of the space.

This may seem a bit complex, but the values are many:

• You know in advance that you will get space -- or that you are going to have to gate check.
• You can board at any time and still get your space. Finally being in first class can mean the privilege of boarding last rather than the strange "privilege" of boarding first.
• Airlines can draw more revenue from people with bigger bags. Well, that may not be a plus for passengers.
• Alternately, airlines can only charge for overhead space if it's in contention. If there's plenty, no need to charge.
• Airlines can allow larger carry-on bags to those who want to pay for them, if there is room.
• As noted, greedy people like me who stick their backpacks and laptops up above only do it if there's room, making more room for you
• In theory, boarding should be faster. Just take your bag to the designated space (Which is visible in your mobile app) and get in your seat.

Downsides include:

• This is complex.
• People will put bags in the wrong space, or put bags that expand beyond their allocated space because they measured wrong. Taking those bags for gate check may cause air-rage. It's probably hard to allocate that freed space to a specific bag to it would become part of the open space.
• Strangely shaped items add complexity. The computer can figure out if they will pack, but will people?
• It's not clear what to do with non-rigid items like coats or other things that can change shape to fit.
• People may get more space than they need, which wastes space compared to the "jam it in" approach.
• Likewise, spare space in non-rectangular items could be wasted -- but then it often is already.

Clothing can usually just be stuffed into the spare space that is left because bins are not regular in shape and neither are items. There would not be space reserved for coats etc. If they don't fit on top of things, they go wherever they can.

Limited reserved bag space

It may be simplest to begin this with a limited amount of reserved space, leaving most of the space "first come first served" as it is today. The space in first class and the section at the front of the cabin reserved for elite or higher paying passengers. This is cheaper, and the space can be clearly marked as "reserved." The flight attendant's computer could tell them what space in the reserved section to allow use of based on who has boarded the aircraft so that nothing is wasted.