Signal flag Sierra

A blue rectangle on white.

Also known as: Sierra flag, Code flag Sierra

Sometimes confused with: S pennant

Maps & navigationSafety & hazardStandard profile

Meanings

The International Code of Signals flag for the letter Sierra, whose single-flag meaning is: I am operating astern propulsion.

Officially standardisedVerified fact
Flown alone, signals: I am operating astern propulsion.
Contexts: Public information, Navigation
Historically documentedVerified fact
The visual inverse of the Papa flag, which is a recognised source of confusion between the two at distance.
Contexts: Public information, Navigation

A white rectangular flag carrying a blue rectangle at its centre.

IdentityHigh confidence: High confidence because the identity is defined by a current official standard.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.

IMO Resolution A.1116(30), Escape route signs and equipment location markings
International Maritime Organization · retrieved 2026-08-22
The resolution text is not reproduced here and has NOT BEEN READ in full. Registered so records can state that a life-saving appliance marking is defined by the IMO rather than by convention, and which broad class it belongs to. See docs/paywalled-standards.md.
ITU Radio Regulations and the maritime signalling appendices
International Telecommunication Union · retrieved 2026-08-27
Cited for the identity of maritime and radio signalling conventions defined by the ITU. Not cited for national licensing arrangements.

Last reviewed 2026-08-27

Meanings

The International Code of Signals flag for the letter Sierra, whose single-flag meaning is: I am operating astern propulsion.

Officially standardisedVerified fact

Flown alone, signals: I am operating astern propulsion.

Historically documentedVerified fact

The visual inverse of the Papa flag, which is a recognised source of confusion between the two at distance.

Confidence

IdentityHigh confidence: High confidence because the identity is defined by a current official standard.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.

Sources

IMO Resolution A.1116(30), Escape route signs and equipment location markings
International Maritime Organization · retrieved 2026-08-22
The resolution text is not reproduced here and has NOT BEEN READ in full. Registered so records can state that a life-saving appliance marking is defined by the IMO rather than by convention, and which broad class it belongs to. See docs/paywalled-standards.md.
ITU Radio Regulations and the maritime signalling appendices
International Telecommunication Union · retrieved 2026-08-27
Cited for the identity of maritime and radio signalling conventions defined by the ITU. Not cited for national licensing arrangements.

Last reviewed 2026-08-27