I vote that the business class cabin does not create a reasonable expectation of privacy. The whole seating area of the plane is a public place. I'm not even sure if DL has a solid policy on passengers crossing cabins, except on inbound US international flights where the TSA forces their hand. In any case, Mr. Kettle does not have a duty to Joe to respect such a rule if it exists, so there's no recourse to him. For DL to be liable, I would say that it's contract with Joe would have to explicitly say that it accepts responsibility for maintaining the privacy of the business class cabin, which it doesn't. I don't buy that a general on-board announcement asking passengers not to cross between cabins counts for anything, either interpreting it as incorporated in the contract between Joe and DL or as a non-contractual promise on which Joe could reasonably rely (promissory estoppel).