Abstract: The invention relates to a process and apparatus for heating the intake air in internal-combustion engines by means of a flame starting system with at least one glow plug. The apparatus is controlled in such a manner that the glow plug is continuously preheated during a first time period and is operated in pulses in a following second time period and the glow plug is switched off after a safety time has elapsed. The glow plug is preheated after it has been switched off, taking into account the instantaneous glow plug temperature during the cooling and the voltage available in such a manner that the temperature required for a repeat start is reached within a narrow tolerance band.