Would a wire that included "Cuba Flight Reimbursement" in a reference field need to be blocked/held. The wire was going from the US to Hong Kong.

that is a pretty broad question, but at a minimum, it would depend on whom was the beneficiary of the Cuba flight...

The wire was from an aviation company in the US to an individual in Hong Kong that chartered a flight to Cuba, The transfer was for a reimbursement of funds due to a flight delay. The money went from the US to the individual from Hong Kong.

The aviation company is subject to US jurisdiction so if it were my customer, I'd ask them what the purpose of the flight was. If it falls under the activities covered by the general license, I'd release the funds. If it was not an acceptable activity, I'd block the funds, etc.