It's still the same case now, Norwegian Airlines doesn't participate in PreCheck (just flew to Europe last week). However, you can sort of mitigate that if you

It's still the same case now, Norwegian Airlines doesn't participate in PreCheck (just flew to Europe last week). However, you can sort of mitigate that if you're also a member of Clear. At my local airport Clear lets me use the PreCheck lines even if the ticket isn't PreCheck (which is contrary to my understanding of how it's supposed to work, but I'm not complaining!).