Lost my phone on aeroplane mode I lost my Samsung s5 on a flight the day before I took the last photos of my honeymoon they are the only ones that are not backed up. Could some one tell me if they will ever be backed up? Or will my phone need a internet signal?
If you had an internet connection when you took the photos, they'll get backed up, assuming Auto Backup was switched on.

Otherwise, the photos will get backed up only if someone finds it and switches on the internet connection. 

Given that you lost the phone in a flight, chances are high that you can find it by contacting the airport authorities.