Solved
The honorarium was $1000, and the flight was around $700. I don't know how to classify the 1099-NEC (a hobby? self-employment?), and subsequently how to write-off the $700 flight which ultimately was not part of my income.
Since you received this for performing a service, if this is done to earn money or on a regular basis, you can enter this as Self-Employment income. When entered as self-employment income, you can deduct the flight and other expenses.
If this is not done on a regular basis or with the intent to earn money, then it would be considered hobby or income not from self-employment. In this case, you cannot deduct the expenses.
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