Comparando el F-35 con todos sus problemas (que no son pocos) y su falta de madurez un 50% MC tampoco parece mal dato comparado con la situación por ejemplo de los EFA alemanes (hasta hace poco tenian solo 4/128), los EFA Austriacos (8 de 15 operativos y tambien problemas con el RWR) o los Rafale M franceses (un 54% hace un par de años segun este medio http://www.air-cosmos.com/les-chiffres- ... vale-85089)
Y estamos hablando de un avión de quinta que esta dando sus primeros pasos... no de un avión civil.
De todas formas el F-35B ha sido probado en combate y durante el despliegue parece que no ha tenido quejas:
On its first combat deployment, the Marine Corps’ F-35 bombed both the Taliban and ISIS
https://taskandpurpose.com/f-35-combat-deployment
Overall, the F-35 exceeded expectations during its first deployment, Shoop said. The squadron was able to keep 75 percent of its aircraft operational at all times, allowing it to "fly pretty much at will."
"A conservative estimate is the F-35 flew 100 percent more hours on this deployment than a typical deployment for a Harrier squadron," [LtCol. Kyle Shoop, CO of VMFA 211] said. "When you consider that their readiness was 75 percent or better ... while doubling the amount of flight hours being flown, it's a real testament to the aircraft and the maintainers."