Been discussed on another thread, YES the first item:
- oxy "ON'; then
- establish comms; then
- .....
Happy to be corrected but I believe Mr Boeing reckons you complete ALL non-normal memory items before moving on to another checklist.
WE manually deploy cabin oxy as a back-up to the auto system, it is part of the non-normal memory items.
Whilst we CANNOT make sure pax put masks on we CAN make sure the masks are available.
If, as Captain/PIC whatever you choose NOT to complete/defer the non-normal memory items AND the auto system fails you WILL be tried for manslaughter at the very least as by the time you have ensured the "...safety of your passengers..." by backing up the auto system (as per that pesky non-normal checklist Mr Boeing have for RAPID DEPRESSURISATION) some/many pax will already be unconcsious and unable to put the mask on.
An EMERGENCY DESCENT with pax oxy on will certainly be unpleasant but survivable, with no pax oxy on will certainly be death for some/many.
Cheers.