What is the difference between the prefixes по and у in verbs of motion

Question

I have been studying Russian for a while and have looked at a number of grammar books for Russian by I fail to see the nuance between 'по' and 'у' For example:

Мой самолёт улетит... vs. Мой самолёт полетит...

Thanks

Answer 1

The prefix По- with verbs of motion has two main meanings 1. Beginning of motion — perfective aspect. Что сделать?(unidirectional) пойти, поехать, полететь, побежать, Куда? К кому? Where? To whom? в, на,к (prepositions used after verbs)

Я пошёл на работу. Машина поехала после остановки. Мальчик побежал. Самолет полетел в Москву. Я полечу завтра.

2. A little bit, for a short while, insignificantly– perfective aspect. Что сделать?(multidirectional) походить, поездить, полетать, побегать Где? По чему? Where? Across what? по (the preposition used after verbs)

Я походил по парку немного. Птицы полетали и сели на дерево.

The prefix У- means 1 Somebody’s absence in the given place, departure from the place. уходить/уйти уезжать/уехать Imperfective/perfective, unidirectional. Откуда? От кого?From where?From whom? из, с, от(prepositions used after the verbs)

Мы улетаем утром из Домодедово. Он улетел, но обещал вернуться. После каникул студенты снова уезжают из дома.

Answer 2

As prefixes for motion verbs, у- usually emphasises on a place from which the motion starts, while по- makes emphasis on a trajectory of motion (implying that the destination is a subject to change, though such a distinction, that is, an uncertain route, is not mandatory). Cf:

Я скоро уеду. (The ellipsis topic is about the place from which the speaker is about to start)/

Я уезжаю сегодня (Again, the speaker emphasises that (s)he is about to part.

Он уехал. (He is no more here).

Я скоро поеду. (I am having a destination to part in the nearmost future).

Я поеду сегодня (I am about to take a new route today; I am going to part today and I want to inform you that I have some destination, though it's not certain).

Он поехал / поехавший. (He's crazy; he's out of common sense).

Hence, Мой самолёт улетит... = My plane is to leave this place..

Мой самолёт полетит... = My plane is about to fly along a trajectory (though it's not a definate one)...

Bot phrases suggest something a little bit extraodinary / unusual about the flight. To describe a regular flight, one might say something like

Мой самолёт улетает /вылетает /вылетел... = My plane leaves this place (as it is usually supposed to fly)