I've rebuilt my airline and reestablished a base in an airport where I had a base before. From the base that I had there before, I had a huge number of slots at this airport. Of course after the rebuild I've restarted my most important routes, but there were still a lot left that I couldn't restart immediately. They had to wait.
Now that I wanted to continue rebuilding my airline and setting up routes that I hadn't set up earlier, I found that at the airport where I previously had hundreds of available slots, that number has suddenly dropped to zero. It seems like I've fallen out of grace because I've rebuilt my airline.
Is the game taking away slots too easily? It seems like it. Slots are too hard to gain and too easy to lose. How can I re-earn those slots if I'm not allowed to expand?