Complex sentence: It was chosen as an ignition method for reliability reasons, because the JP-7 fuel has very low volatility and is difficult to ignite and classical ignition plugs posed too high risk of a malfunction.
Split into simpler sentences: It was chosen as an ignition method for reliability reasons, because the JP-7 fuel has very low volatility and is difficult to ignite. Classical ignition plugs posed too high risk of a malfunction.