Transitioning from an IFR flight plan to an oceanic route is a relatively simple procedure when crews plan for this transition. The oceanic clearance should be received, verified and accepted long before the aircraft approaches the oceanic boundary. En route charts contain the appropriate frequency to request the oceanic clearance, but experienced international crews already have the frequency noted on their flight plan along with the appropriate position when the controlling agency may first be contacted. Prior preparation is critical when operating in international airspace.

A professional flight crew should be able to copy and read back an oceanic clearance without a misstep. Oceanic clearances contain an entry point, en route waypoints consisting of latitude and longitude positions, the exit point, a clearance altitude and a Mach speed to be flown while within the airspace. Even if the aircraft is cleared to fly a specified track, the controlling agency requires a read-back to include each waypoint on that track.

When requesting an oceanic clearance, the crew must compute an estimated time of arrival (ETA) at the oceanic entry point by factoring in the estimated time en route (ETE) from the master flight plan and convey that ETA to the clearing authority.

Clearance is usually received from air traffic control (ATC) approximately 200 mi. before reaching the gateway fix when flying eastbound from North America. If a clearance has not been received when the flight is within 20 min. of the fix, the crew must call the appropriate agency (Gander, New York, Shanwick or Santa Maria Oceanic Control) on either VHF or HF and request the oceanic clearance.

During westbound flights from Europe:

North of 50 deg. N. Lat. — Contact Shanwick before 02 deg. W. Long.

South of 50 deg. N. Lat. — Contact Shanwick before 01 deg. W. Long.

South of 45 deg. N. Lat. — Contact Santa Maria OAC at least 20 min. before crossing the OAC boundary. Contact Santa Maria radio on HF. Pertinent information on clearances can be found on the Atlantic (H/L) 1 en route chart.

In 2006, nearly 400,000 flights crossed the North Atlantic, making that airspace some of the busiest in the world. Since normal land-based communications and radar surveillance are not available over the North Atlantic, horizontal and vertical separation of aircraft is ensured through a strict set of parameters and procedural disciplines.

Clearances for Pacific crossings are usually received on the ground prior to takeoff. If the clearance is delayed until after the aircraft is airborne, as is the case in the Atlantic, the clearance must be received before the aircraft crosses the oceanic entry point.

A good pre-departure technique when conducting oceanic operations is to test the HF radios long before takeoff. At minimum, before entering oceanic airspace, the crew must perform a functional test of HF radios, and ensure that all navigation equipment used for the trip is in working order.

Mach number technique must be used for all oceanic operations. The controlling agency can only plot the approximate position of aircraft, based on position reports. Pilots must maintain their Mach number within a tolerance of +0.01, unless a change is granted by ATC. After leaving oceanic airspace, the pilot is expected to continue to fly the flight plan Mach number until ATC authorizes a change in airspeed. Pilots must notify oceanic control if their ETA at the next reporting point changes by +3 min. when operating on a designated track, or by +5 min. when operating off the designated track system.