Growing fees leave airline passengers annoyed

The latest airline tactic: charge extra for an aisle seat.

I know this gets people upset, but I think it's just the natural extension of the principle of supply and demand. In fact, I would price the economy seats on a three-tiered system if I owned an airline: middle seat cheapest, then window, then aisle. Nobody wants the middle seat, so why not charge less for it?

But I would add this: once everyone is seated and the plane is in the air, the flight attendants need to relax and let people move from the center seats to the aisle if the aisle seats happen to be empty. It doesn't make sense to have two people crammed into the center and window seats while the aisle seat is unoccupied.