I’m posting to see if this has been a thing or is a new thing, currently anytime I enter a flying vehicle, armed or not my passive mode is disabled with a message that says “Passive mode is not available is this type of vehicle”. I don’t remember this being part of the game on next gen consoles but I’ve been off of GTA for a while as well.
I’m guessing it’s new with the update. I’ll edit my post and let you know if I’m having the same issue. I’m on 360 though.
Edit: I’ve been able to go in passive mode in both the pilot & passenger seats in the Swift Deluxe
This update sucks, all my cars are gone 
I don’t think it would be on last gen because of the whole not a ghost thing but do give it a try and let me know!!!
How?
I had the monkey blista, lost slamvan, dukes o death, a hearse with no casket, a insured BMX in a car slot, and a few others. All gone…all my money got wiped too, I’m left with 50k. I had about 7.5 mil before the update…R* ruined my online experience, once again…
Exactly, next-gen. consoles have a different Passive Mode then those playing on the Xbox 360 or Playstation 3.