OBS_VALUE: Slots are allocated in a fair, non discriminatory and transparent manner, following the principle of equal oportunities to all airlines.The general principle regarding slot allocation is that an air carrier having operated its particular slots for at least 80 % during the summer/winter scheduling period is entitled to the same slots in the equivalent scheduling period of the following year (so called grandfather rights). Consequently, slots which are not sufficiently used by air carriers are reallocated (the so called use it or lose it rule).