Why did they use vertical trade lanes?

[Lord Caedus]

Oh also I forgot to mention that if we follow the same logic used for aircraft, if you have an issue with your ship and fall out of the trade lane, you can't accidentally drift into oncoming traffic as long as the pilot only turns left or right. Same reason that when aircraft are in danger of a potential collision, they all only turn the same direction horizontally without pitching up or down.

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