Jetpack Cheat Code for GTA IV (Xbox 360)?

No jetpack cheat exists in GTA IV. The jetpack (Jetpack / Thruster) was a GTA: San Andreas feature. GTA IV removed it for realism.

GTA IV Cheats (Xbox 360) — For Reference

Enter via in-game phone → Dial:

• Full Health/Armor: 362-555-0100
• Weapons Tier 1: 486-555-0150
• Weapons Tier 2: 486-555-0100
• Remove Wanted Level: 267-555-0100
• Raise Wanted Level: 267-555-0150
• Spawn Annihilator (heli): 359-555-0100
• Spawn NRG900 (bike): 625-555-0100
• Change Weather: 468-555-0100

Warning: Using cheats disables achievements/trophies for the session. Save beforehand.

For jetpacks, play GTA: San Andreas (cheat: LEFT, RIGHT, L1, L2, R1, R2, UP, DOWN, LEFT, RIGHT on PS2/PS3; Y, B, LT, LB, RT, RB, UP, DOWN, Y, B on Xbox).