International signals used by ships at sea, used to spell out short messages, or used individually or in combination each with a special meaning. Also used to dress a ship for ceremonial and festive occasions (protocol) There are also numeric pennants, answering pennants

A-Alpha	B-Bravo	C-Charlie	D-Delta	E-Echo
diver below (when stationary);  I am undergoing a speed trial	I am taking on or discharging explosives	affirmative	keep clear of me, I am maneuvering with difficulty	I am altering my course to starboard

F-Foxtrot	G-Golf	H-Hotel	I-India	J-Juliet
I am disabled, communicate with me	I require a pilot	I have a pilot on board	I am altering my course to port	I am going to send a message by semaphore
K-Kilo	L-Lima	M-Mike	N-November	O-Oscar
you should stop your vessel instantly	you should stop, I have something important to communicate	I have a doctor on board	no (negative)	man overboard
P-Papa	Q-Quebec	R-Romeo	S-Sierra	T-Tango
all aboard, vessel is about to proceed sea.  (At sea) your lights are out or burning badly	my vessel is healthy and I request free practique	the way is off my ship. You may feel you way past me	my engines are going full speed astern	do not pass ahead of me

U-Uniform	V-Victor	W-Whiskey	X-X-ray	Y-Yankee
you are standing into danger	require assistance  (not in distress)	I require medical assistance	stop carrying out your intentions and watch for my signals	I am carrying mail
Z-Zulu		repeater 1	repeater 2	repeater 3
to be used to address or call shore stations		The first repeater repeats the upper flag or pennant of a hoist, the second repeater repeats the second flag or pennant, and so on.
Click here to spell anything and see the Nautical Flag equivalent