Riding a Pelican

Watch YouTube video on how to "Ride a Pelican" 8s1o7HKmPFA On some levels it's possible for a player to climb or jump on top of a Pelican and ride the ship to its destination.

Metropolis
Play through the Metropolis (Level) until you get to the part where you're in a Gauss Warthog with another Warthog riding alongside you (your situation may be slightly different, but that's what is meant to happen). You come into a street with a couple of Jackal snipers, two Wraiths, and a couple of Ghosts. Another Wraith and two Phantoms come momentarily, followed by two Pelicans.

Notice where the Jackal snipers were standing: raised areas between the streets. Go to the far one. This is the point where the Pelican will drop off some marines for you. Be at the top of this area before the Pelican begins its descent.

As soon as the marines have exited the Pelican, jump toward the passenger bay and hold the X button. I suggest aiming for the bottom of the Pelican, right near the back entrance. If you don't feel like timing a jump or just can't do it, hijack a wraith and place it where the marines are dropped off, climb on the wraith and wait for the pelican. This should allow you to climb in the cargo bay and go for a ride.

After a short trip, the Pelican falls to the bottom of the level. In Halo: Combat Evolved, a free-falling Pelican would travel the exact same path every time, but things might be different here. When I did this in single-player mode, two marines, the Pelican, and I all landed safely at the very bottom of the level. In the three times I've tried it in co-op mode, though, everybody landed on a giant concrete platform (too far down to get back into the level, and too far up to continue to the very bottom). The Pelican continued its way down, while we were stuck there. Sometimes instead of landing on the giant concrete platform, you land on a invisble platform which is below the giant concrete platform

Outskirts
Also, if you jump onto the rooftops at the beginning of the Outskirts (Level) and completly blow off the battle in the first part, a checkpoint will appear and Sergeant Johnson will spawn and begin boarding a Pelican which will also come. If you jump onto the Pelican it will fly off with you on it. You won't get far though because it disappears in mid-air!

Delta Halo
Another example is on the level Delta Halo, where you continue as normal until the pelican comes in and drops off the Warthog. Get to where the Shade turret on a small hill was and then wait for the Pelican to come to a halt. Then Grenade jump up to the Pelican. It will fly around with you on its back and then move forward faster making you drop down to your death.

Assault On The Control Room
At the beginning of the level a Pelican will drop you of and as soon as you are droped of it will say " HOLD X TO RIDE PELICAN". If done successfully you will be able to ride it for a short time. At the end of the ride though you will die. Although it is possible to survive if you are playing on co-op mode and one person gets out of the Pelican.

Pelican rotates, passing through solid ground
Watch the Pelican spin and pass through solid ground (Around 50sec mark) NPhKsY9ZLHY If you manage to get to the bottom (blue area), you notice two pretty interesting things. The first is that the Pelican lands facing up, or keeps rocking back and forth until it looks straight up. The second is that when you walk up to it, it says, "Press X to flip Banshee." even though the vehicle is a Pelican and not a Banshee.

Then if you press X it flips end for end and if you time it right it will hit you and send you flying into the air. The scarab gun cannot be obtained if someone gets hit by the pelican. The one on top of the bridges is too high up (even if the Sputnik skull is activated) and too (horizontally) far away. The fall timer would kill anyone trying to get the other scarab gun.

Also if you are lucky you can get the Pelican to end up as though it had landed perfectly, you can get into it and go all the way through to the pilots seat and press X. You can now fly the Pelican as though it were a Banshee. It looks pretty cool having a pelican doing barrel rolls and flips!!