Last week the USAF tested one of their F-15 fighter jets with an alternative synthetic fuel for a cleaner ride. The fuel was a 50/50 blend of JP-8 Jet Fuel (Kerosene based) and a Natural Gas based synthetic. The test consisted of a 50 minute ground test and a 55 minute flight where they pushed it to Mach 2.2, or about 1500 MPH (Mach is a relative speed depending on altitude and air temperature). According to Maj. Dan Badia, one of the test pilots, "You could have had JP-8 in there and I wouldn't have known the difference."
The Air Force has been testing synthetic blends on cargo jets & bombers since 2006 but this was the first fighter jet flight fueled by the blend, showing that it can stand up to the performance rigors of the aircraft.
This was part of the USAF's plan to move their entire fleet to synthetic fuel by 2011. The advantage to Natural Gas based synthetic fuels are that they burn much cleaner and we have a stable domestic supply. It does have some drawbacks.
First off, it is still a non-renewable fossil fuel. Environmentalists are split on this issue as it relates to auto, some arguing that it's a cop out, and others arguing that it is a practical transition fuel to help move us away from petroleum based fuels. In the context of the Air Force, I think it's a good step considering we are not likely to see any Plug-in Hybrid Fighter Jets in the next couple years.
Another concern critics have is that these synthetics can also be created from coal which is much cheaper than natural gas. Some fear that the we'll end up going the cheaper route and end up using coal. There is a considerable amount of controversy over how clean coal based synthetics are, many argue that they will produce significantly more CO2 than their petroleum based counterparts.
While this may not do anything to help solve global warming, it is an important step in showing that we can transition to cleaner options and will hopefully serve as a stepping stone to a transition to a renewable fuel like algae.