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Gift card purchases are no longer reimbursed for any airline. There are ways to use gift cards to create a transaction that may be reimbursed, but not all airlines sell gift cards.

Airline lounge memberships and passes are reimbursed, for the airlines which operate them: AS, AA, DL, UA.

Note that there is a separate discussion thread for each airline. Questions about what works, and how to structure the transactions, are almost certainly already answered:

Alaska Airlines
American Airlines
Delta Airlines
Frontier Airlines
Hawaiian Airlines
JetBlue Airlines
Southwest Airlines
Spirit Airlines
United Airlines