raraoul

And between seasons of the same year? I can understand that there is more demand to the south of Europe in the months June-August than in December-February..

What kind of benefit do you have being the launch customer? It's none.. 

2nd, if you dont pre-order, you still have youre money and that money you can invest in aircraft that are already being produced -> thus you get more aircraft -> thus increase in earnings way before youre pre-order aircraft is on the list.

What does it makes sense to pre order aircraft? There is no difference between ordering an aircraft 1 year before its launch date or ordering it 1 day before, right? 

Airbus:

A319: Alitalia

A320: Air France, Alitalia, Easyjet, Lufthansa, Edelweiss Air, Wizz air

A321: Air France, Swissair

A340-300: Air Mauritius

Boeing:

B737-700: KLM, Transavia

B737-800: KLM, Ryanair

B737-900; KLM

B747-400: KLM

B777-300ER: KLM, Air France

B787-800: KLM

Bombardier:

CRJ700; Lufthansa

it is the price per seat.

Take a look at the forum posts and you get a better idea how to start and operate a profitable airline.