Æ - Currently the one I visit the most but mostly for the community. The airline bit's pretty good, I guess.
Cyber Airlines - >:c is all I have to say for that monstrosity.
AirwaySim and that other paid one - not paying for airline stuff, not worth it
Airline Mogul - It felt so sloooooow. Not entertained at all with this one.
Airlines Manager 2 - It's in French but thanks to Google Chrome that's not really an issue. Has a lot of features and overall is the best airline game I've played... (sorry Yuxi!)
Airline Manager (the Facebook one) - Entertained for a while-ish.
myairline.it - Don't touch this one. It is scum.