R Lebowitz 10-min lecture Dec 29, 2009. As he quips “here is the STANDING psak of many gedolim”: (each line below has a page reference that I omitted).
Standing – to have better kavana, or as a servant, like bringing karbonos, Avraham stands “amida”
you can sit on a donkey and daven (Rebbe, brochos), on a boat (brochos 30a) because it is scary, shaky. Getting off the donkey prolongs the trip. You can make donkey go 3 steps back. Standing will ruin kavona. On a wagon, if you can – stand, if not – sit. S’A If you daven sitting, then re-daven standing. M’B says no.
on plane – R Moshe: if you daven sitting on the plane, do not repeat later, better to sit to begin with, but get up for bowing. R Wosner paskened for El Al’s Rabbi to direct passengers to daven in place and not do minyanim. R Auerbach – daven sitting on a plane, not to stand – you will be distract and distract others.
Davening on a bus – not proper, just to save time. R Kanevsky allows getting off a bus when you are davening (including – it is better to continue davening off the bus!). So, if stewardess tells you to sit – you just sit down and contiue davening.