A special formulation of jet fuel
used in high-temperature military
applications, such as in the SR-71 Blackbird
This wide-cut non-kerosene fuel has a higher flash-point than typical turbine fuels, meaning that it must be raised to a much higher temperature, in the presense of oxygen, before igniting. JP7 is rare, and good data about its properties are hard to come by. One source puts its ignition temperature at 1200 degrees F. In theory, you should be able to drop a lighted cigarette or a match into some JP7, and it would not ignite. Many technicians had a lot of fun by performing this stunt at the feet of startled visitors.
JP7 fuel is so difficult to ignite in the engine, that a chemical called triethylborane is required to kick-start the process. Nevertheless, in the SR-71 Blackbird, the fuel tanks are inerted with nitrogen because of the extreme ambient temperatures during sustained supersonic flight.
In addition to the high flash-point, JP7 is formulated in such a way that extreme heat does not degrade the fuel. Other fuels, such as JP5, JP8, or Jet-A1 would turn to sludge if subjected to these high temperatures for a sustained period.