President Bush said other steps were under consideration to reduce crowdedskies, such as charging airlines higher landing and takeoff fees at peak hours, and auctioning off landing and takeoff rights to the highest bidder.
The decline in travel because of the recession made airports and the skies less crowded, reducing flight delays and cancellations when bad weather or other problems forced airlines to thin out schedules.
As the skies become more crowded, technology could be used to enable the size of such "safety spheres" to be reduced - or rather, to allow planes to fly closer to each other.
So although there are azure skies on the distant horizon, in the short range the airspace is getting crowded with new competitors and new planes, and there may not be enough business to keep them all flying.