European transport ministers have provisionally agreed to allow airlines to buy and sell airport slots, although the proposed regulation still has to be approved by the European Parliament.
In a European Council meeting in Luxembourg this week the ministers outlined several measures to allow secondary slot-trading in a bid to address capacity demands.
Under the proposal airlines will be permitted to trade slots but also face the prospect of fined for returning unused slots to the pool too late for re-allocation.
The proposal will allow member states to enforce temporary restrictions on slot-trading if demonstrable problems arise - although these must be transparent and proportionate, and the European Commission will have the right to oppose them.
These measures follows some of the delegations' seeking "safeguards" to protect less-profitable regional services, says the Council, and expressing concern over the "potential speculative use" of traded slots.
But the European Commission and others, it adds, underlined the need for "uniform application" to avoid fragmentation of the market.
The resulting draft regulation has been amended to produce a "compromise acceptable to the majority" of delegations.
While the Commission has reiterated its plan to raise the minimum threshold for slot use from 80% to 85% - the 'use it or lose it' criterion - a large majority of member states have opposed changes to the slot-allocation system which grants priority to incumbent carriers.