India has notified a temporary danger zone of about 600km in the Bay of Bengal for 25-26 September. The window from 03:30 UTC on the 25th to 10:30 UTC on the 26th. The Ministry of Defence has not named the missile. Range corridors of this size fit several systems in the inventory the notified distance is a safety parameter. Launches of this kind usually leave Dr A.P.J. Abdul Kalam Island or the Chandipur range and fly south-east over water. Ships and aeroplanes are told to stay out. That is the defence notice. It is also a civil-aviation alert.
Bay of Bengal tracks carry traffic between Kolkata, Chennai, Port Blair, Bangkok, Kuala Lumpur, Singapore and points further east. A danger area from the surface to unlimited altitude forces dispatchers to file around it or delay the sector until the NOTAM expires. Fuel and crew legality follow the longer line. Neighbouring flight-information regions like Yangon, Bangkok, Kuala Lumpur, Colombo need the same coordinates if a reroute clips their airspace. Coordination is supposed to happen through ICAO channels before the first aeroplane is airborne. When it is late, the first the airline sees is a pink notice and a dispatcher rewriting a night sector.
India will keep using this stretch of sea. The test calendar is becoming part of how the eastern seaboard’s airspace is managed with a two-day window, airlines that already know the Odisha overlay. The collision is not dramatic. It is a Tuesday morning in which a Kolkata-Singapore flight burns extra fuel because a range is live. Mapping the affected city pairs and the hours they cannot use the great-circle is more useful than guessing the warhead.
A NOTAM of 600km says less about the missile than about how much of the bay India is prepared to close. Civil operators should treat the next one as routine infrastructure, and plan the long way round.