I am going to Eretz Yisrael during the Nine Days. Can I wash dirty pjs and towels for the trip?
The prohibition against washing clothing in the days before Tisha Bav is split into two parts. The first part is from the Rosh Chodesh Av until Shabbat Chazon, the second part is from Shabbat Chazon until Tisha Bav. Sfardic custom is not to wash clothing during the second part, while Ashkenazim extend the prohibition to include the first part of the nine days. During the days before Tisha Bav one may not launder clothing or towels at all, however it is permitted to use fresh towels. If all of one’s clothing has become so dirty that it is unwearable, they may wash clothing to wear (פתחי תשובה יו”ד סי’ שפא ס”ק ג).
If you have nothing clean that you can wear on the trip, you may wash the clothing. However, if there is any way to avoid washing and wearing freshly laundered clothing, you must avoid washing.
The Kaf Hachaim (תקנא א) writes that one who is very careful with the halachot of Tisha Bav and the Days preceding it will merit to see the miracles of the times of Mashiach. Have a safe flight!