I think we'd be surprised how many on the corporate dime are ENTITLED to First Class and (their companies) pay for it.
The account for the US Government alone in all its guises flying around big shots and senators, ambassadors, and congressmen would be enormous, and I doubt you'll ever see them in coach! That dollar input alone would probably justify the airlines keeping it on.
If an Aussie businessman buys a business class ticket SYD-NYC or MIA or BOS etc (as virually EVERY half senior exec is automatically entitled to as part of their job contract) you are (on United anyway) almost always in First acorss the USA as the bulk of UA domestic are 2 classer 757/737/767 and Airbus etc.
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~ Glen ~