I don't think I have to explain what this trick does; it lets Warthogs and other vehicles fly. It's kinda easy, but you'll see that when you start reading this tut. New detail is that it's now for PAL. Not entirely by me (winks at Iron_Forge), but I did the testing and stuff. OK, without further notice, let's begin.

STEP 1 - Get the cache003.map from your Xbox (Y:\-partition).

STEP 2 - Open it up with a Hex-editor, in this example, we'll use Hex Workshop 4.10.

STEP 3 - Go to Edit, click on Goto. Fill in 2340658 in the bar, make sure Hex is on instead of Dec. Click Go.

STEP 4 - When it has found it, replace 889D8A80 with 84128F80.

STEP 5 - Now go to Edit, and again, click Goto. Now fill in 282D9A0 and click Go again.

STEP 5.1 - Replace

01 00 00 00 08 AC 9C 3E CD CC CC 3D D0 44 58 3B 58 39 34 3C 00 00 10 42 00 00 10 C2 00 00 80 3F 00 00 34 43

with

05 00 00 00 AE 47 61 3E 00 00 00 00 6F 12 03 3C 6F 12 83 3C F9 0F C9 3F 00 00 00 00 00 00 00 00 CD CC 4C 3E

Step 6 For Scorpion goto offset 023414D8 and replace with 84 12 8F 80 then goto 28605E0 and type

Step 7 - 05 00 00 00 AE 47 61 3E 00 00 00 00 6F 12 03 3C 6F 12 83 3C F9 0F C9 3F 00 00 00 00 00 00 00 00 CD CC 4C 3E

Step 8 - For ghost just goto offset 287EBD8 and type

05 00 00 00 AE 47 61 3E 00 00 00 00 6F 12 03 3C 6F 12 83 3C F9 0F C9 3F 00 00 00 00 00 00 00 00 CD CC 4C 3E

STEP 9 - Now save your file, and transfer it back to your Xbox on the Y:\-partition. Boot up Halo again, and you should be fine. Fly safely!
Source: Xbox-scene.com