I am a 20 year old girl travelling on a short flight (about 3 hours) on a small air-plane. I think I will be the only Jew, and the rest of the passengers will be non-jews. It could be that there will not be so many passengers. Is there a problem of Yichud, and if yes, how many non-jews are needed to take away the Yichud problem?
If there are only a few people on the flight, then it would be a problem of yichud according to many poskim, but if there are many people there then it is considered like it is a public domain, (reshus horabim) and it wouldn’t be yichud. It is hard to give an exact number at which point it turns into a public place, if there are 20 people on the flight it would be alright.
Chut Shani Yorah Deah -3 pg. 207, Ohel Yackov Yichud pg. 552 in the name of R’ Y. Belski, R’ Y. Cahen shlita. There is an opinion that in such a situation that she may use her phone to video herself, and even though it is controversial if a live video (that someone can see what is happening in real time) can prevent yichud, in this case we can be lenient.