Probably it is the best hidden secret kept in this city!! I have been there this November and It's annoying trying to travel from the city to the airport. There are just two options: taxi or bus. Taxi is quite expensive but definitively the best way!
Nobody knows and there's not any sign about where the bus stop is in Midi (Midi Station). When you finally guess where to go, probably will find a queue big enough to miss the bus. Yes, the only one bus goes every 30 minutes. The joke is the bus will not arrive on time!!
Make a rush and arrange by your self a group of desperate tourists to pay together for a taxi. Party of 8 is the best, is more o less €15 per person, the same for the bus. You could find volunteers very interested among the disappointed people in the queue!!