You can install new interiors at any time, it's just not worth it for old planes with a limited future (because they're gas guzzlers). Planes can essentially f

You can install new interiors at any time, it's just not worth it for old planes with a limited future (because they're gas guzzlers). Planes can essentially fly indefinitely if you're willing to put money into ongoing maintenance. For instance some B-52s will have served for roughly 100 years by the time they are retired.