Your friend needs to contact the Guatemalan embassy (or consulate nearest him), and the airline considered to determine what is needed.

As well, your friend will have to be able to satisfy the Transportation Security Administration of his status to fly.

Acceptable IDs include:

"We understand passengers occasionally arrive at the airport without an ID, due to lost items or inadvertently leaving them at home. Not having an ID, does not necessarily mean a passenger won’t be allowed to fly. If passengers are willing to provide additional information, we have other means of substantiating someone’s identity, like using publicly available databases.

Passengers who are cleared through this process may be subject to additional screening. Passengers whose identity cannot be verified by TSA may not be allowed to enter the screening checkpoint or onto an airplane <link>.

• U.S. passport
• U.S. passport card
• DHS "Trusted Traveler" cards (NEXUS, SENTRI, FAST)
• U.S. Military ID (active duty or retired military and their dependents, and DOD civilians)
• Permanent Resident Card
• Border Crossing Card
• DHS-designated enhanced driver's license
• Drivers Licenses or other state photo identity cards issued by Department of Motor Vehicles (or equivalent)
• A Native American Tribal Photo ID
• An airline or airport-issued ID (if issued under a TSA-approved security plan)
• A foreign government-issued passport
• Canadian provincial driver's license or Indian and Northern Affairs Canada (INAC) card
• Transportation Worker Identification Credential (TWIC)

"

As well, the airline employees may be sticklers for some acceptable documentation; we can't have a clue if "some other documents" qualify or not.

N/B. This is in the Other Asian, Australian and South Pacific Frequent Flyer Programs Forum, an unlikely place to get this answered; I will ask a Moderator to move this to a more appropriate Forum,