Just checked my airlines...
AirNZ from 24 hours before, but not essential
KLM from 30 hours before, will be at sea then, maybe possible when we get close to land.
Ryanair, surprise, from 60 days before, no problem.
Singapore from 48 hours before, will be on land then, so no problem.
I'll install the apps from all of these on my already over-apped phone.
Would be worthwhile for someone to develop a check in app that worked
for all airlines.