Turns out the supply chain for such a complex machine is in itself very complex. Some components are manufactured by suppliers in various countries formerly believed to be allies. This includes stuff like the ejection seats and some electronics that are made in the UK, parts for the wing sets that are made in Italy or inserts for the weapon bays that are made in Canada. Additionally the Netherlands currently houses the supply hub for spare parts for the European countries. It is estimated that there are spare parts to keep hundreds of F-35s in the air for a while there. The most worrying aspect certainly remains the software support, without which all the precious hardware loses much of its utility, even if there isn't a master kill switch.