It’s also not uncommon for unpressurised aircraft to be operating at 14,000ft or above in PNG due to the high LSALTs and grid heights throughout the highlands.
Certainly was the case in my all-too-short time in that place!
Still remember sitting at 16,500' in an A mod C402 for about two and a half hours on one trip. The a/c did have an O2 bottle but it was empty! And I had previously asked for it to be refilled.
Landed back at Moresby with an 'altitude headache'.