ON COURSE-
a..
Used to indicate that an aircraft is established on the route centerline.

b..
Used by ATC to advise a pilot making a radar approach that his/her aircraft is lined up on the final approach course.

(See ON‐COURSE INDICATION.)
ON‐COURSE INDICATION- An indication on an instrument, which provides the pilot a visual means of determining that the aircraft is located on the centerline of a given navigational track, or an indication on a radar scope that an aircraft is on a given track.
ONE‐MINUTE WEATHER- The most recent one minute updated weather broadcast received by a pilot from an uncontrolled airport ASOS/AWOS.
ONER-
(See OCEANIC NAVIGATIONAL ERROR
REPORT.)

OPERATIONAL-
(See DUE REGARD.)
OPPOSITE DIRECTION AIRCRAFT- Aircraft are operating in opposite directions when:
a..
They are following the same track in reciprocal directions; or

b..
Their tracks are parallel and the aircraft are flying in reciprocal directions; or

c..
Their tracks intersect at an angle of more than 1350.

OPTION APPROACH- An approach requested and conducted by a pilot which will result in either a touch‐and‐go, missed approach, low approach, stop‐and‐go, or full stop landing.
(See CLEARED FOR THE OPTION.)
(Refer to AIM.)
ORGANIZED TRACK SYSTEM- A series of ATS routes which are fixed and charted; i.e., CEP, NOPAC, or flexible and described by NOTAM; i.e., NAT TRACK MESSAGE.
OROCA- An off‐route altitude which provides obstruction clearance with a 1,000 foot buffer in nonmountainous terrain areas and a 2,000 foot buffer in designated mountainous areas within the United States. This altitude may not provide signal coverage from ground‐based navigational aids, air traffic control radar, or communications coverage.

OTR-
(See OCEANIC TRANSITION ROUTE.)
OTS-
(See ORGANIZED TRACK SYSTEM.)
OUT-The conversation is ended and no response is expected.
OUTER AREA (associated with Class C airspace)-Nonregulatory airspace surrounding designated Class C airspace airports wherein ATC provides radar vectoring and sequencing on a full‐time basis for all IFR and participating VFR aircraft. The service provided in the outer area is called Class C service which includes: IFR/IFR-standard IFR separation; IFR/VFR-traffic advisories and conflict resolution; and VFR/VFR-traffic advisories and, as appropriate, safety alerts. The normal radius will be 20 nautical miles with some variations based on site‐specific requirements. The outer area extends outward from the primary Class C airspace airport and extends from the lower limits of radar/radio coverage up to the ceiling of the approach control's delegated airspace excluding the Class C charted area and other airspace as appropriate.