Sidetracked

Sidetracked is a heist setup mission in Grand Theft Auto V. It is required to begin the obvious approach in The Big Score heist.

Overview
Lester will send a text message to all the protagonists saying that he got an aerial crane to steal the train, one of them needs to divert the train in Davis Quartz and another one needs to use the Skylift to steal the train wagons and take it to Sandy Shores Airfield.

Mission
First use stealth mode to knock out the two guards that are guarding the railroad. Then go to the cabin and switch the train tracks to divert the next train. Once the train has arrived, the protagonist (Michael or Franklin), will call Trevor to tell him that the train is ready; if Trevor is the protagonist who diverted the train, he will call Michael. Switch to Trevor and use the magnet in the Skylift to steal the freight engine and any of the flatbed carriages and deliver it both in the Sandy Shores Airfield.

To collect the carriages, fly the helicopter directly above the carriage and paralleled to it. Once close enough to it, press the required button and the magnet will pull it.

Mission Objectives

 * Knock out the guards at the railroad.
 * Switch the train tracks.
 * Wait for the train.
 * Steal the freight engine.
 * Take the freight engine to Trevor's airfield.
 * Put the freight engine in the back of the truck.
 * Steal a flatbed carriage.
 * Take the flatbed carriage to Trevor's airfield.
 * Put the flatbed carriage in the back of the truck.

Gold Medal Objectives

 * Time - Complete within 04:30.
 * Use the sniper rifle to get rid of the guards, then use a vehicle to move around the quarry. Fly low in the chopper when retrieving the cars.
 * Undetected - Steal the train without being detected.
 * Use a melee weapon, sniper rifle or suppressed weapon to incapacitate the guards.

Trivia

 * It's not possible to keep the Skylift after the mission is completed (if updated).
 * This mission is vaguely similar to The Ballad of Gay Tony mission For the Man Who Has Everything, as it requires one person to unhook a train car and fly away with the train carriage in a Skylift. In TBOGT, the player has to withstand a five star wanted level, but in V, there is no wanted rating. In TBOGT there is only one carriage, but there is two that are taken in V. The Trains are different due to TBOGT variant being a subway car and the V variant being freight train carriages and the cab.
 * Franklin is the only character who won't fly the Skylift. There are three ways:
 * If Michael or Franklin start the mission, Trevor will fly the helicopter.
 * If Trevor starts the mission, Michael will fly the helicopter.
 * Trevor will respond badly if Michael knocks out the guards, but will be more pleasant if the player picks Franklin.
 * In real life, the events of this mission would not be possible. The real Sikorsky S-64 Skycrane can only lift about 12 tons. A large diesel-electric locomotive weighs in the range of 200 tons.
 * Also, no practical electromagnet can lift anywhere near that much weight. If it could, the power supply alone would outweigh the helicopter's lifting ability.
 * If the mission is started as Franklin and failed as Trevor, Michael will be at the cabin instead of Franklin.