Quick answer
The X-40 Nightmare is a fictional stealth fighter that debuts in ACE COMBAT 8.[1] You meet it first as an enemy: in Mission 29, "Selene" (Operation Lunar Eclipse), the enemy Selene flies an X-40, and that encounter is automatic.[2]
To fly it yourself:
- Finish the campaign.
- Buy one of three jets: the F-22A Raptor, F-35C Lightning II or Su-57 Felon.
- Spend 1,000,000 MRP on the X-40 in the Aircraft Tree.[1]
Unlock path, step by step
| Step | What you need | Source |
|---|---|---|
| 1 | Complete the campaign. The X-40 shows up on the Aircraft Tree after that. | Community wiki[1] |
| 2 | Own one of: F-22A Raptor, F-35C Lightning II or Su-57 Felon | Community wiki[1] |
| 3 | Pay 1,000,000 MRP | Community wiki[1] |
Do you need Elite difficulty? The sources word this differently.
- PowerPyx's S-rank guide says that clearing the campaign on Elite unlocks Ace difficulty, "the overpowered endgame aircraft (FA-36 and X-40)", and Free Mission.[3]
- PowerPyx's trophy roadmap adds that if Elite is too hard, you can play a lower difficulty first "to unlock the end-game planes".[4]
- The community wiki only says "after completing the campaign".[1]
Read together, a campaign clear on any difficulty appears to be enough for the X-40. Elite is needed for Ace difficulty, not for the plane. See Ace difficulty unlock.
The 1,000,000 MRP price and the three prerequisite jets come from a single community wiki page, checked on October 1, 2026. We will recheck them against the in-game tree. The full tree is on aircraft tree unlocks.
What the cost means in practice
KeenGamer estimates that a full campaign run pays 3 to 4 million MRP, depending on how well you play.[5]
Our calculation:
- 1,000,000 ÷ 3,000,000–4,000,000 means the X-40 costs about 25% to 33% of one campaign's payout. That is before you buy the prerequisite jet, whose price we have not confirmed.
- Against the 25,000,000 MRP lifetime trophy goal, the X-40 is 4% of the total.[6]
To earn the MRP faster, see MRP farming.
X-40 loadout and strengths
| Weapon | Count (community wiki) |
|---|---|
| Gun | ∞ on Easy/Normal |
| MSL (standard missiles) | 154 |
| UAVT | 16 |
| EMLB | 18 |
| QAAM | 18 |
| Flares | 3 |
The community wiki lists the role as Multirole, with these weapons.[1]
- Best use: PowerPyx calls the X-40 the usual pick for S-rank runs. It works well on most missions, and its UAVT special weapon hits both air and ground targets.[3]
- Weak spot: UAVT ammunition is limited. On missions with clusters of ground targets, PowerPyx recommends switching to a plane with area-effect air-to-ground weapons.[3] More options are on best planes.
- Trophy: the X-40 is on PowerPyx's list of aircraft verified for post-stall maneuvers, which the "Like the Wind" trophy needs.[4]
"Nightmare" is also a trophy name
Do not mix up the plane and the trophy. "Nightmare" is also the Bronze story trophy for completing Mission 26, Crossing Fleets.[6] The mission where you fight the X-40 is Mission 29, "Selene".[2] Both are in the full mission list.
Not confirmed yet
We found no written, bylined guide to the Mission 29 X-40 fight itself, so we give no boss steps here. For score tips, see S rank requirements.
Sources & References
- Ace Combat Wiki (wiki.gg): X-40 Nightmare (edited Oct 1, 2026) ↩ 1, 2, 3, 4, 5, 6, 7
- PowerPyx: Ace Combat 8 All Assault Records & Enemy Aces (Sep 29, 2026) ↩ 1, 2
- PowerPyx: Ace Combat 8 All Ace S-Ranks Walkthrough (Oct 1, 2026) ↩ 1, 2, 3
- PowerPyx: Ace Combat 8 Wings of Theve Trophy Guide & Roadmap ↩ 1, 2
- KeenGamer: ACE COMBAT 8: WINGS OF THEVE – All Missions List (Rafly Wibowo, Sep 29, 2026) ↩
- KeenGamer: ACE COMBAT 8: WINGS OF THEVE – All Trophies List and Platinum Roadmap ↩ 1, 2
