Tomorrow's WSJ has a big story about the rapid deployment of nat gas trucks in the USA. This year, only 1% of trucks sold in America run on nat gas; next year it will be 5%, and the big uptrend is likely to continue. CNG is the equivalent of $1.50/gallon cheaper than diesel.
To read the story, google: "Truckers Tap Into Gas Boom".
This development is definitely favorable to the airlines because jet fuel and diesel are basically the same product so, presumably, there will be more supply for airlines if truckers use less. Logically, you should also see a fall in oil prices on this development -- truckers use 20% of all fuel consumed in the USA -- but the financialization of the oil market makes price predictions based on supply/demand extremely unreliable.
FWIW, long term I'm skeptical about converting trucks from diesel to natgas because I think diesel is the better fuel and -- absent financialization -- the price of the two fuels should be equivalent. But, as we've seen, Wall Street has a bizarre impact on the oil market, and anyone betting on real supply/demand to determine price has been wrong for a decade..
Cheap gasoline and diesel are subsidized by $100+ billion in the US (we have teh cheapest fuel for any oil importing nation except for Egypt & Indonesia) BUT CNG pays no road taxes at all, as the truckers tear up the roads.