[QUOTE=Efrem;12668303]I had a consulting gig once that was going to pay for a business-class USA-France round trip. I asked the client if it would be OK for me to buy an economy ticket, upgrade it with miles, and bill them for the J fare. They OK'd it, so I did. (As it happened, I only upgraded the return, since I knew the BOS-CDG flight would be nearly empty and I'd be able to get five across to lie down.)
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If I read this correctly, the idea was to buy an economy ticket but charge the client for a J ticket. Maybe I'm misunderstanding, but I don't see how that would be reasonable. If I were your client, I'd say no way, and I'd start taking a close look at any other expenses you submit.

More reasonable would be to charge the client for the Y ticket and the upgrade fee.