Actually, the entire set-up is in flux. One poster noted that newspapers and magazines have been able to count the copies supplied to airlines (and hotels) in their circulation. Basically, the higher the circulation the higher the rates magazines and newspapers can charge advertisers. However, in the advertising arena there are two main types of circulation - paid and controlled (free). Paid is typically thought of as you pay to subscribe to a magazine or newspaper or you buy it at a newsstand. For what it's worth, media buyers typically believe that is stronger that controlled as they know the person wanted the magazine or newspaper as they bought it.
Most of the magazines and newspapers you see distributed by airlines or hotels were being counted by the publishers as paid, however, they really weren't. What was happening went something like this: Airline X wants to buy $1 million of advertising in The Daily Daily Newspaper. As most publishers discount, they end up agreeing to pay $600,000 in cash and $400,000 in subscriptions. For the publisher, they get $400,000 in additional subs they can count as paid subscriptions and the airline gets "free" newspapers and magazines for their customers.
What's changed is the main auditor of magazines and newspapers has decided these really aren't paid copies and should be classified as controlled - public place which means the publisher can count them in their circulation but not as paid.
The number of copies each title was putting out as controlled but previously counting as paid was released for the first time about a month ago, so media buyers for the first time are seeing these numbers. I believe it was reported in one of the ad trades that Time Magazine had over 1 million public place copies. These also count places such as doctors offices (in these cases the copies are usually sponsored by pharm companies, etc.).
If media buyers discount this public place circulation, or in other words tell publishers they will not pay high rates based on this circulation but only count paid circ, over time you will see publishers supplying less of these copies.
As to publishers paying to be on planes, this is true too. Many airlines don't want to get involved in the logistics of supplying themselves with the reading material so they appoint a third party vendor that then charges the publishers a handling fee. The airline still chooses what titles are on what flights but the third party is responsible for coordinating shipments from the publishers and then supplying them to lounges and aircraft.