OPENING (n)  An "aperture" or hole in a surface   MAKE SURE THE OPENING IS CLEAR.  
 operable (adj)  OPERATE (v)  MAKE SURE THAT THE VALVE CAN OPERATE.  Check that valve is operable.
       MAKE SURE THAT YOU CAN OPERATE THE VALVE.  
 OPERATE (v), OPERATES, OPERATED, OPERATED  To put, keep, or be in "action"  OPERATE THE PLUNGER TO DRAIN THE SYSTEM.  
 OPERATION (n)  That which occurs when something operates or is operated  PUT A WARNING NOTICE IN THE FLIGHT COMPARTMENT TO PREVENT THE OPERATION OF THE SYSTEM.  
 operational (adj)   SERVICEABLE, OPERATE (v)  MAKE SURE THAT THE OTHER MICROSWITCH IS SERVICEABLE.  Check that the other microswitch is operational.
       MAKE SURE THAT THE GROUND-PROXIMITY WARNING SYSTEM CAN OPERATE.  Check that the ground proximity warning system is operational.
operator (n)  PERSONNEL  PERSONNEL MUST KNOW ABOUT THIS EQUIPMENT BEFORE THEY USE IT.  Operators must be knowledgeable about this equipment prior to use.
 OPPOSITE (adj)  1. In the other direction  THE RESET DEVICE OPERATES IN THE OPPOSITE DIRECTION.  
    2. Across from  THE BOLTS ARE ON THE OPPOSITE SIDE OF THE FLANGE.  
 OPPOSITE (pre)  Across from  THE UNIT IS IN THE WHEEL BAY OPPOSITE THE LANDING GEAR.  

 
 
 option (n)  POSSIBLE (adj)  IF POSSIBLE, DO THE INSPECTION IN DAYLIGHT.  If you have the option, do the inspection in daylight.
 OPTIONAL (adj)  Not mandatory  THIS TOOL IS OPTIONAL.  
 OR (con)  Function word that shows a "choice"  DO NOT TOUCH THE HIGH TENSION LEADS OR THE IGNITER PLUGS.  
 order (n)  SEQUENCE  DO THE WEIGHING PROCEDURE IN THIS SEQUENCE:  Carry out the weighing procedure in the following order:
 order (v)  ORDER (TN), TELL  SEND AN ORDER FOR THE SPECIFIED PAINT DIRECTLY TO XXXX.  Order the required paint directly from XXXX.
       TELL ALL PERSONNEL TO GO OUT OF THE MAINTENANCE AREA.  Order all personnel out of the maintenance area.
 orient (v)  TURN, POINT  TURN THE AIRCRAFT INTO THE WIND.  Orient the aircraft into the wind.
       POINT THE BOLT HEADS AFT.  Orient the bolt head aft.
 origin (n)  SOURCE  THE SOURCE OF THE PROBLEM IS IN THE FUEL SYSTEM.  The origin of the problem is in the fuel system.
original (adj)  FIRST (TN), INITIAL  THE FIRST MODIFICATION INSTALLED A XXXX.  The original modification installed a XXXX.
       THE SLIDE GOES BACK TO ITS INITIAL POSITION.  Slide returns to original position.