My nonreligious grandma is having a 90th birthday party in Florida during the nine days. Can I fly out to be there even though it’s the nine days? (I live in New York)
You may fly there. Although we are careful not to do dangerous things during the nine days, it is controversial if flying nowadays is considered dangerous or not, especially because it is only a domestic flight. This is coupled with the fact that what you are doing can be considered a mitzvah. Therefore it is permitted.
Kovetz Halachos (Bein Hamityzarim) 7-3,