According to the Delta rules page, your account can be terminated — and your miles forfeited — in any of the following cases: Fraudulent activity on your account. You request account closure. Death of the Delta SkyMiles member.

In 2026, Delta SkyMiles never expire, so if your balance has dropped to zero or disappeared, it is likely due to a specific "High-Fidelity" administrative event rather than simple inactivity. The most common reason is that you may have accidentally created a duplicate account, and your miles are sitting under a different SkyMiles number. Another high-fidelity possibility is that Delta deactivated the account due to suspected fraudulent activity or a violation of the program's terms, such as the unauthorized sale or barter of miles. If an account remains inactive and the member does not respond to repeated communications, Delta also reserves the right to close it. Finally, if you recently redeemed miles for a "High-Fidelity" award but the trip was cancelled, the miles should have been redeposited; if they weren't, a technical glitch may be the culprit. It is a high-fidelity requirement to contact Delta's customer service with your name and address to help them locate and merge any split accounts or investigate a missing balance.