Looks like it all comes down to $$$-- with them ignoring, of course, the LAW$UITS they will get the next time one or two planes crash during one of the "high-severity errors" described below. And this was all before gas prices were at the level that they are now...God knows what other changes they will make to "save fuel, save money".
http://www.cnn.com/2005/TRAVEL/01/21/air.traffic.separation/The new rule reduces the long-standing vertical separation minimum of 2,000 feet to 1,000 feet, thus doubling the number of routes airlines can fly between 29,000 feet and 41,000 feet, an FAA press release said.
"This action ... gives pilots and air traffic controllers more choices to allow aircraft to fly more direct routes at the most fuel-efficient altitudes," FAA Administrator Marion Blakey said in a statement.
"When you save fuel, you save money: it's that simple. And more efficient routes save the passenger time."The agency estimates that this move will save airlines and other aircraft operators at least $5.3 billion over the next decade." From 1998 to 2003, incidents of aircraft coming too close together increased 34 percent.
In 2003, an average of three operational errors occurred each day, with one high-severity error every seven days.