DL9921 LondonLHR SeattleSEA
DL9921 by Delta Air Lines flies from London (LHR) to Seattle (SEA).
scheduled from LHR
The route today
live boardsWeather lens
Delay & cancellation outlook for this flight
Measured, 90-day sampleConditions at LHR and SEA are near their clear-air norm right now, so this reflects the route's recent baseline rather than a weather penalty. For this route and airline, under conditions like today's, over the last 90 days.
Pro Flight Search tracking, 90 days · the weather × delay correlation study → · live weather risk by airport →
When it flies
scheduled departuresEach mark is a scheduled departure at its origin-local time. Today is highlighted.
Other London to Seattle flights today
same route · Delta Air LinesIf DL9921 is cancelled, this is the other Delta Air Lines nonstop flight from London to Seattle on the same day, with scheduled departure times in LHR local time. Most flights posting a delay still operate — rebooking usually only beats a very large posted delay. Every airline on this route →
How DL9921 actually runs
Pro Flight Search has tracked every published board update for DL9921 across the LHR and SEA boards: schedule changes, gate pushes and actual clocks. Combined risk score: 50.0/100. Based on airport operations, weather, and cached board history at LHR and SEA.
The verdict above is that record speaking, so it reflects how DL9921 operates rather than what the timetable promises. Numbers refresh as new flights operate.
Planning around DL9921? Will a delayed flight be cancelled? · Do planes make up time in the air? · How we measure
Journalists, bloggers, and researchers may cite this page with attribution and a link to Pro Flight Search.
Pro Flight Search — DL9921 London to Seattle on-time performance, measured from the LHR and SEA airport boards.
https://proflightsearch.com/flight/DL9921
.