FWIW: It’s important to remember that O’s air department acts primarily as a Travel Agent selling air tix. And once you book through O, it takes on responsible for necessary tix changes. What lot’s of folks don’t realize is that any fare differences/penalties for those changes depends on whose issue is the change required:
Disembarkation port change - O issue.
Airline cancel/bump/etc - airline issue.
Your change (e.g., late airport arrival) - your problem.
In all cases, O as your air TA will assist w/ re-ticketing. But, O will only pay for their own problems. Note, however, that this often also includes necessary tix change fee reimbursement for DIY O passengers when O changes start/stop ports.
We were on Nautica’s final pre-Covid cruise in early 2020 ending in Dubai instead of Singapore. For us DIY air folks, O provided no cost satellite phone service to make air changes and provided up to $250 pp for associated air tix changes.
In another different cruise situation, exec concierge assisted with language translation related to our DIY air concerns when Max 8 planes were grounded.
Nonetheless, we still always DIY air -particularly for Bizclass (which even O’s Air Dept will tell you not to use O air since you receive no credit for the economy tix paid for in the original cruise fare [still required to get the Bizclass quote from them])