If one is riding on a DONKEY [comparable to a car today], he/she does not need to come off the donkey to pray--EVEN if there was someone who would hold onto his donkey--rather he/she prays while travelling (=דרך הלוכו)
If one is travelling on a BOAT or a CARRIAGE [comparable to a Bus or an Airplane], if one can stand for the Amida, then stand; if one cannot stand, then he/she just sits in his place and prays the Amida.
If one is traveling on FOOT, one may pray (amidah) as one walks, even though one is not facing toward Jerusalem, even if not in a place of danger, for if one would stand and pray, the delay in his journey would cause one difficulty and DISTRACT ONE'S MIND so that one would not be able to concentrate. Each situation should be judged according to the journey, the location, one’s particular anxieties and peace of mind.
(Shulhan Arukh Siman 94:4)
If one is travelling on a BOAT or a CARRIAGE [comparable to a Bus or an Airplane], if one can stand for the Amida, then stand; if one cannot stand, then he/she just sits in his place and prays the Amida.
If one is traveling on FOOT, one may pray (amidah) as one walks, even though one is not facing toward Jerusalem, even if not in a place of danger, for if one would stand and pray, the delay in his journey would cause one difficulty and DISTRACT ONE'S MIND so that one would not be able to concentrate. Each situation should be judged according to the journey, the location, one’s particular anxieties and peace of mind.
(Shulhan Arukh Siman 94:4)