If you clear, It's going to take more than one sticker. That's a 4 or 5 sticket route.
You're right. My brain translates stickers to be "SFO-JFK" stickers - I think in blocks of 6.
Actually, the site says right now that I need 0 upgrades to upgrade. That's probably a bug.
Finally, thanks for prompting me to check again, I found that 25E opened up since I last checked! Moving forwards...