Originally Posted by
ExXB
Yet, your contract remains with the airline whose code you are booked under.
The contract may be with the marketing airline, but it's for carriage on the operating airline.
If and to the extent that the contract includes specifying the cabin baggage allowance, the contract provides that your cabin baggage allowance is that of the operating airline. The marketing airline has not promised you that you will get the cabin baggage allowance which would apply if you were to fly on a flight operated by the marketing airline.
The DOT's issue seems to be whether this (if it is a contract term) and other provisions similarly incorporated by reference are made sufficiently clear by a generalised statement by the marketing airline. Nowhere can I see any hint that the DOT considered that if the marketing airline sells a flight on a different operating airline, the marketing airline must promise you the same cabin baggage allowance as would apply if you were to fly on a flight operated by the marketing airline, regardless of the operating airline's limits.
That would just be wishful thinking.