Two runways side by side can only send planes off at the same time if the planes go different ways. It’s a safety rule, from ICAO, the international aviation body. After take-off, the tracks have to split.
That’s what a second runway is for at the busy times: more departures, off both runways at once. Capacity. Which means the split isn’t something you add for the neighbours. It comes with the capacity.
The rule says the tracks must diverge. Remember that word. It doesn’t say which one has to turn.
In 2016 daa consulted the public on the North Runway’s routes. Its display panels said international standards require the planes to diverge by at least 15 degrees, “approximately one nautical mile after take-off”. The maps showed a gentle 15-degree split, because that was “the minimum requirement”.
In 2017 daa’s noise consultants wrote it up. The Aviation Authority, they said, would require a divergence of 15 degrees or more. The turn would come at about a mile from the end of the runway, which they “considered the earliest point that a turn is likely to be possible”. That mile was their assumption. The ICAO manual says “immediately after take-off”.
Thirty degrees appears nowhere in anything the public was shown.
In August 2022 the runway opened. The planes turned, early, by 30 degrees, and some by 75. The neighbours had been shown 15 degrees at a mile, and 75 for some (story 2 has those). Never 30. They got 30 at a few hundred feet.
Where did 30 come from? It’s in the same ICAO manual. A different chapter, for a different reason: if a plane landing on one runway has to abort and go around, it must not run into a plane taking off from the other one. So the go-around and the departure must split by 30 degrees.
Must split. Not: the departure must turn.
In November 2023 the Aviation Authority wrote to an Oireachtas committee. “In principle, the missed approach procedure for 28L could turn left to ensure a divergence of at least 30 degrees from aircraft departing on runway 28R which continue straight ahead.”
Straight ahead. As assessed. As permitted.
In March 2026 the Authority’s witness said it again, to the committee’s face. The go-around could turn 30. Or each could turn 15. “There are many different ways to do it.”
But by the time it reached the Department of Transport, the rule had already been rewritten, in English. In April 2023 the Minister’s officials, passing on what daa and the Aviation Authority had told them, explained it to his office: “To operate parallel runways safely, flightpaths must diverge by a minimum of 30 degrees northwest after take-off.”
Northwest. The ICAO manual has no compass in it. Somewhere between Montreal and the Minister’s office, “diverge” picked up a direction, and the direction was over the houses.
So, here’s where we’ve landed. A safety rule says two tracks must part. The rare plane that aborts a landing could do the parting. Or the two could split it between them. Or the departures could part through the gaps between the towns instead of over them. The regulator says there are many ways to do it. Day after day, the departures do the turning, over people nobody asked about these routes.
The rule never said who had to turn. Somebody decided it was you.
Sources
- International Civil Aviation Organization (ICAO), Manual on Simultaneous Operations on Parallel or Near-Parallel Instrument Runways (SOIR), Doc 9643, Second Edition, 2020: Chapter 3 (independent departures, tracks to diverge by at least 15 degrees “immediately after take-off”) and Chapter 4 (segregated operations, a departure track to diverge by at least 30 degrees from the missed approach track of the adjacent approach); the First Edition, 2004, has the same two provisions. Available from ICAO by title
- daa, public consultation “Consultation on Flight Paths and Change to Permitted Operations”, display panels and brochure, October 2016 (15 degrees “approximately one nautical mile after take-off”; maps illustrated at 15 degrees “as this is the minimum requirement”). Reproduced in Appendices A and B of daa’s report on the consultation, February 2017: https://www.dublinairport.com/docs/default-source/north-runway-downloads/public-consultation-report–flight-paths-and-change-to-permitted-operations.pdf?sfvrsn=b06d628_2
- Bickerdike Allen Partners for daa, Dublin Airport North Runway: Investigation into Noise Impact of Potential Departure Routes, report A9843-R04-DC Final, 12 July 2017 (the Aviation Authority’s requirement of 15 degrees or more; the turn at about 1 nautical mile, “considered the earliest point that a turn is likely to be possible”). Released to NRTG under AIE request 2615 (daa), on internal review, 7 August 2026
- AIP Ireland (published by the Irish Aviation Authority, now by AirNav Ireland), Dublin Airport Runway 28R standard instrument departure charts, EIDW AD 2.24-13.1, as published for the North Runway’s opening in August 2022 (turns of 30 degrees, and about 75 degrees on some routes, from the end of the runway) and as revised in 2023. Current edition: https://www.airnav.ie/air-traffic-management/aeronautical-information-management/aip-package; NRTG holds copies of the 2022 and 2023 editions
- Irish Aviation Authority, letter to the Joint Committee on Transport and Communications, “Flightpaths at Dublin Airport”, 7 November 2023 (“In principle, the missed approach procedure for 28L could turn left …”). NRTG holds a copy
- Joint Committee on Transport, evidence of the Irish Aviation Authority, 24 March 2026 (“There are many different ways to do it”). Official report: https://www.oireachtas.ie/en/debates/debate/joint_committee_on_transport/2026-03-24/
- Department of Transport, email from officials to the Minister’s office, 26 April 2023, relaying information provided by daa and the Irish Aviation Authority (“flightpaths must diverge by a minimum of 30 degrees northwest after take-off”). Released to NRTG under FOI request FOI-2025-0110 (Department of Transport), 24 July 2025