Thank you for the warm welcome and helpful tips, I would like to share my experience and data point for the flight I booked:

1. Wednesday, October 9, 2024:

- Read on a Facebook post that Delta is having Business Class Flight Award sale for multiple countries on selected date.
- Found a perfect flight to South Korea on my birthday for 100,000 miles (with 15% award sale from Delta Credit Card)+ $5.60 in taxes.
- Applied for Delta Gold Credit Card and got approved right away, but I could not access to the temporary credit card information even with the help of customer support as they told me to wait for the physical card to arrive (which it arrived on October 16, 2024). I kept trying until I got home and accessed to home’s wifi then I finally have access to the temporary credit card information.
- I added the Delta Gold Credit Card information in Delta’s wallet and the 15% award sale was applied.
- Since I did not have any miles in my Delta account I transferred 200,000 Amex Points to Delta with $99 fee. I was able to use the miles immediately and booked 2 one-way tickets to South Korea on Delta One. Statement on Amex Plat was 2 Delta Airline $5.60.
- I did not want to use points to book for the return flight, so I paid cash which was ₩780,000 ($569.34) + ₩153,500 ($112.04) per ticket. I assumed I would receive the full $200 Airline Fee Credit as the taxes for 2 people exceeded $200. Statement on Amex Plat was 1 DeltaAirlines DeltaRepublic of Korea KO $1,362.76

2. Sunday, October 13, 2024:

- Amex’s Airline Fee Credit meter moved to $11.
- I contacted Customer Support to request Airline Fee Credit for my return flight, but it was denied as they claimed it was not fit to any of the categories.

3. Monday, October 14, 2024:

- I received 2 Airline Fee Credit of $5.60 since I booked for 2 people.
- I decided to use the method in the thread for the remaining Airline Fee Credit and succeeded on October 19, 2024 as mentioned above.