Runaway Train
When the team reaches North Corel, head down the tracks to the Corel Reactor. They reach it just in time to watch Shinra drive away with the Huge Materia in the back of a train. Fortunately for the team, Cid can drive anything, so they steal a train and chase the Shinra train.
To catch up to the Shinra train, you can alternate the levers left (D-Pad up) and right (A {triangle}) to speed up the train and align it with the enemy train. Try to get a slow rhythm going, and then build up your speed.
Note:
Remember, you only have 10 minutes to catch the enemy train, board it, and then reach the cabin and stop it before it crashes into North Corel.
An enemy, each one tougher than the last, protects each train car. It's important that you make quick work to them so that you have plenty of time left when you reach the engine.
Car #1: Gas Ducter
Easy fight; hit it hard with anything but Bio.
Car #2: Gas Ducter (x2)
Same as first one, but twice as tough.
Car #3: Wolfmeister
Susceptible to water; use the enemy skill Aqualung or the summon Materia "Leviathan". You can poison it, but it may not help much.
Car #4: Eagle Gun
Use Bolt spells against it; avoid casting Earth or Water spells on it.
Engline: Attack Squad
This thing isn't tough. Hurry through the conversation before the fight. There's no time to waste!
Now you must stop the train. Move both levers down and then up, alternating back and forth until the train stops.
With the train stopped, Corel is saved and you've received your first piece of Huge Materia. As a dept of gratitude, the people of North Corel give you the "Ultima" Materia. Now hop back in the Highwind and head for Nt. Condor.
Note:
If you failed to save North Corel, you not only lose the Huge Materia but you'll have to pay 50,000 Gil for the "Ultima" Materia!