Small-hours departures:
Sometimes they were the result of route licensing restrictions. In about the mid-80s, Britannia managed to get route licences to both Malta and Cyprus, after endless objections by their home-based airlines. This was long before the current era of unrestricted routes for EU airlines.
One of the licenses - I think it was Malta - included a condition that departure from the UK had to be within some deeply unfriendly time bracket, something like 0001 to 0400. This was, of course, an attempt to protect the traffic of the home airline.
There were other reasons, too. For example, Corfu at that time was limited to daylight ops only, so there were occasionally Britannia rotations that were timed to get there at first light. That meant leaving LTN at something like 0100. Lovely. Around the end of the 80s there was a slight improvement to the approach lights at Corfu, and night ops were deemed to be acceptable. So the silly times departures ended, but night arrivals at CFU could be less than a barrel of fun, especially when CBs were banging around the place.