Dum Dum: A series of checks, technical drills and best practices is preparing the airport for the launch of the CAT III-B instrument landing system on Thursday, coinciding with a projected fall in temperature and possibly also fog.

The airport expects flight delays caused by fog to go down by at least 50 per cent once the new instrument landing system is switched on. Delays can be cut further if all airlines deploy pilots trained in the use of the CAT III-B system on aircraft operating to and from Calcutta whenever there is fog, an official said.

Precision landing with a lower visibility limit of 50 metres will become possible after CAT III-B is operational. The CAT II instrument landing system currently in operation enables aircraft to land till a visibility cut-off of 350m. This is inadequate in Calcutta, where visibility often dips much lower in winter.

Airport officials have been running technical checks on taxiways and also the centreline lights, another crucial component of the new system. The lighting along the centreline of the primary runway has been doubled.

A meeting was held recently to identify parts of the runway, taxiways and surrounding operational areas where vehicle movement is restricted. When CAT III-B is in operation, any construction activity or other such work will be suspended. The authorities would also need to ensure that there is no equipment lying around the path of aircraft.

"If visibility is low on January 4, flights will be able to land using the new system," airport director Atul Dixit said on Tuesday.

Pilots trained in CAT III-B procedures have been practising landing in low-visibility conditions for a month. Airport officials said there had been 60-odd such landings with CAT III-B in the past 30 days.

"For most of the time, visibility during fog is between 100 and 200 metres. Operational efficiency and reliability will go up by more than 75 per cent (with CAT II-B)," said Captain Sarvesh Gupta, chairman of the airline operators' committee at the airport.