Signal Flags P – Papa and S – Sierra

The International Code of Signals encompasses 26 “Letter” flags, 10 “Number flags” and 4 additional flags for use when used in sequence. Each flag has an independent meaning, and then together, additional messages. 

The signal flags PAPA – “P” and SIERRA – “S” are color inverses of each other. The six-foot rectangular flag (blue with white square) PAPA signals that all personnel should report on board for they are about to set sail. The four-foot square flag (white with blue square) SIERRA signals that the vessel is operating with astern propulsion. Together the two flags signal to nearby ships that they should not come any closer.

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