Most travellers will either depart from central Europe, or use central Europe as a intermediate landing. For Morocco, there should be a good chance of getting last seat tickets at heavily discounted prices. As for which airliners having the cheapest fares, it appears that North African companies are the most expensive, and not among the best, yet the price differences here are often only marginal. There are no clear winners in the price battle on North Africa. Trips to southern Spain can be had at the best prices in April and May, which happen to be the best time to visit.
Chartered trips can be ubelievably cheap.
At the time being no other country in the region of Miftah Shamali are served by chartered trips, yet there are organised trips for Mauritania, that are generally of high quality and at high prices. Organised trips for Libya does exist as well, but these depend on travellers first getting to Tunisia or Egypt, and then crossing the border into Libya. Ferries in the Mediterranean are shamelessly overpriced. The only ones not digging too far down into your pockets run between Morocco and Spain, but these take normally only 1-2 hours. Algeria has rediculously overpriced ferries, never cheaper than a regular airliner.