Question: 1. Because of his experience making his own films, he was hired as a script supervisor by Cathay Studios. **Soon afterwards**, Woo was able to start directing.

	2. Because of his experience making his own films, he was hired as a script supervisor by Cathay Studios. **Soon**, Woo was able to start directing.
	3. Because of his experience making his own films, he was hired as a script supervisor by Cathay Studios. **Afterwards**, Woo was able to start directing.

Answer: 
The first one is more correct. When in doubt, try to split the sentences into parts:

> 
> At what time does [the next plane to London] leave?
> 
> 
> 

The subject in this sentence is "the next plane to London" - which is a perfectly correct way to distinguish it from both "the next plane to Madrid" or "the last plane to London". It's clear you're asking about the first plane which leaves for London, skipping all the other planes which leave for different destinations. On the other hand:

> 
> At what time does [the next plane] leave (to London)?
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> 
> 

The subject is "the next plane" - without any other qualifier, it would mean the first departing plane, without any concern for the destination. And you're asking when that particular plane leaves to London - to which the answer might be "it doesn't", if the plane is going somewhere else.
I agree with @maciej-stachowski that the first version is better, and I agree with their analysis of that version's syntax. *the next plane to London* is what you're asking about, and it's the plane that is flying to London soonest from your location.

I also think that answer makes a good point that *the next plane* by itself would refer to whichever plane is going to leave the soonest (regardless of destination). The phrasing of your second version with *to London* at the end is awkward and doesn't sound quite right. However, I think that if you replace *to* with *for* you will get a valid question that is equivalent in meaning to your first version:

> 
> At what time does the next plane leave **for** London?
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> 
> 

Normally, a vehicle (or person, or whatever) leaves *for* a particular destination (though they go *to* a destination, and maybe the word *going* is implicit in the phrase *the next plane to London* => *the next plane [going] to London*). I think you can ask the question this way and it will be understood that you're only asking about planes that are supposed to fly to London. That being said, I think a simpler way to phrase this question would be:

> 
> When's the next plane to London?
> 
> 
> 

If you were to ask this, it would be understood that you were talking about the departure time (as opposed to the arrival time).