High quality EVs are already extremely unlikely to catch fire. Much less likely than ICE cars of similar model and age. And those cars are exposed to relatively rough conditions (accidents, debris on the road, etc) , and the battery packs aren’t closely monitored.
For a plane, the QA of the battery pack would likely be better to begin with. They’d have much stricter procedures for monitoring the battery packs for possible abnormalities. And they’re unlikely to be exposed to a physical accident.
By the time they hit the skies (2030+) our experience with batteries will also be better. It’s obviously possible to ensure a battery never spontaneously ignite. Most battery packs, by far, never do. We’ll probably have a better understanding of the triggers of freak spontaneous fires.
Even in the ridiculously unlikely event of a battery fire I’m pretty sure it can be handled. People make out EV battery fires to be impossible to handle but the fire departments in places with high EV concentration has it pretty much figured out now and consider EVs to be less problematic than ICE. (Norway, Netherlands)