Far more fuel woud be saved if
1. the american carriers would be forced not to fly aircraft older than 20 years
2. the silly practice of pushing back from the gate in US airports on time even though it is known that the aircraft is not allowed to depart because of bad weather enroute or at the destination. Its a tragedy to see atleast 2-3 aircraft standing in the deicing bay at every major american hub waiting for the go from ATC.