Alan Levine from Illinois wrote:
My parents recently flew to Israel on El Al. The airplane was very full and they ended up having to sit in the back in the smoking section and unfortunately had a very bad flight. On top of the smoking and the people marching back and forth to the bathrooms - just when my mother had finally fallen asleep - the people started davening Shacharit [praying the morning service]. My dad said it bothered them and woke my mother up. He said it wouldn't have bothered them if it'd just been quieter. My question is this: Can I pray sitting in my seat if I feel more comfortable? I think I would be able to concentrate better and it wouldn't bother anybody.
According to the Shulchan Aruch, someone traveling in a ship and unable to stand may pray while sitting, but must pray over again when he reaches his destination. (Today, however, due to our low level of concentration during prayer, we wouldn't pray over, but rather would rely on the sit-down prayer.)
On a 'jumbo jet', though, there are places where ten or more can stand and pray together, while following common courtesy: Pray quietly, avoid stepping on toes, don't block the bathroom or aisle, etc.
To find out El Al's official policy towards in-flight prayer groups, I called their assistant director of public relations. The official told me, "El Al is a Jewish airline. We have never stopped this [people praying with a minyan] ... We do know that people are complaining about this." If enough people were to congregate and cause a noticeable weight imbalance, the captain would be obligated by international aviation regulations to disperse them, said the official, but this never actually happens.
I asked Rabbi Chaim Pinchas Scheinberg, shlita, if one should pray with a minyan on an airplane. He said yes, adding that he does it "all the time." While strictly speaking it might be permitted to pray at your seat, Rabbi Scheinberg prefers that one pray with a minyan, but quietly in a way that doesn't disturb others.
True story: Two rabbis I know were flying from one city to another somewhere in America's 'Wild West'. Heavy turbulence caused one passenger --- a first-time flyer --- a great deal of fear and anxiety. Just as the flight attendant succeeded in reassuring him that all was normal, it came time for afternoon prayer. The rabbis got up, put on their hats and jackets, and headed towards the back of the plane. Seeing this, the frightened passenger became hysterical, saying, "You see! You see! Those guys are getting off!"
- Shulchan Aruch Orach Chaim 94:4,9