After travelling in Europe for 26 years I think that I understand the basics: Needing to be ready to go at the whistle + a landing slot identified and matched before departure. This often entails being 'banged up' for extended periods of time. Hence I always travel with a bottle of water and a flapjack to see me through these delays.
The reference to 'fixed slot' comes from a story that circulated during their brief life. It was stated that they paid a lower landing fee by dint of allowing their slot to be moved, if others with agreed slots were delayed. This may well be an urban myth, which is why I asked if someone might want to comment. I may yet get an answer.
If I failed to ask the question politely enough, then I apologise.
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A window seat on the sunny side of the aircraft, please!