BFI Traffic Management Tips

• BFI is located 5 miles North of SEA, directly under the final approach course or departure corridor for SEA.
• Arrival or Departure rates at SEA may be affected by the absence of Plan Alpha or Plan Bravo at BFI.
• These plans call for BFI Tower to provide visual separation between SEA aircraft and BFI aircraft.
• North Flow departure rates for SEA are adversely affected due to constraints for separation between SEA arrivals, BFI arrivals and BFI departures with SEA departures.
• This may also cause the SEA and BFI AAR to decrease as departure demand increases. Decreasing the AARs at both airports help to mitigate departure delays and surface constraints.
• The AAR for SEA is kept higher than BFI which could see a rate as low as 4.
• If SEA regains the ability to maintain visual separation between their departures and BFI arrivals, the BFI AAR will be increased as BFI arrivals no longer impact SEA departures.

PUGET SOUND CONVERGENCE ZONE

• A local weather phenomenon called “Puget Sound Convergence Zone” produces a strong tailwind to an abrupt headwind on final to RWY’S 16 and can cause up to 3 miles of compression between successive arrivals.
• A "Split Flow" configuration can be associated with the Convergence Zone requiring BFI to be in a North flow and SEA to be in a South flow.
• The convergence zone typically starts in the north and moves south resulting in the winds reaching BFI prior to SEA due to the geographical locations of the airports. This can create a “Split flow” situation where SEA and BFI are landing/departing opposite directions.
• Historically Split Flow is usually very temporary, lasting less than an hour.
• Both SEA and BFI AARs may be adjusted down to accommodate opposite direction operations.
• Airborne holding should be expected.

WINTER STORMS

• Winter storms can produce southwest wind velocities that exceed 100 knots on downwind and up to 60 knots on final.
• This much wind can cause the aircraft on downwind to be up to 200 knots faster than the aircraft on final.
• The length of final becomes the issue due to the speed differential, compression and slow ground speeds.
• In some instances, this much wind can cause an AAR as low as 24.

HIGH SPEED TURNOFFS

• RWY16L/34R does not have high speed turnoffs.

SNOW AND ICE

• All rates may be impacted by snow or ice, on and around the airport, common in the late fall, winter and early spring months.
• Expect runway and taxiway closures for deicing or snow removal.
• Arrival rates may be lowered when the Port of Seattle initiates their “Icing Threat Management Plan” to accommodate the perishable nature of deiced aircraft taxing for departure.

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Page last modified: 06/11/2025