Fighter jets in general are a constant maintenance marathon. They are pushing the edge of engineering and performance. That means that they are less reliable and more expensive to maintain than a 777 by a wide margin. However, the F-35 is significantly more reliable than it's predecessor the F-16.

The F-35 represents the result of a changing model for warfare. Less dogfights and missile duels, more managing a fleet of strike drones, loitering ordinance, ECM, and acting as an observability platform. With the advent of extreme long range, datalink guided, air breathing, air to air missiles, BVR is transitioning to over the horizon combat. I see you, I kill you. F-35 is a reaction to that.