Six of the seven conveyor belts at Calcutta airport's departure area malfunction three to four times a week, sometimes delaying flights as airlines are forced to manually haul luggage from the check-in counters to the baggage segregation area.

The glitches in the conveyor belts, which carry luggage from the check-in islands to the basement four levels below, often take time to fix. On Thursday, the baggage handling system at check-in island B, from where SpiceJet and GoAir operate, malfunctioned.

Airline officials said there were instances of flights getting delayed because of this, apart from inbound passengers not getting their checked baggage after landing.

Once a passenger deposits checked baggage at the counter, it is put on the conveyor belt and carried down to the basement where the baggage segregation area is located. There, every piece of baggage for a flight is identified and put on the trolley that will take them till the aircraft's cargo hold.

It takes about three minutes on an average for a piece of baggage placed on the conveyor belt to reach the basement.

When a belt malfunctions, airlines need to deploy loaders to manually carry the baggage and put them on trolleys. By the time a trolley reaches four levels down on an elevator and is pushed to the baggage segregation area, around 10 minutes are lost on an average.

The baggage handling system at the integrated terminal, which became operational in March 2013, has been plagued by problems from the start. Over the past few months, the glitches have become frequent, airport officials said.

The conveyor belts in the check-in islands used by IndiGo, Jet Airways, SpiceJet, GoAir and Air India have had the most number of breakdowns. Those in the international section have faced fewer glitches, sources said.

Siemens installed the conveyor belts that are part of the baggage handling system at the new terminal. Each assembly comprises a rubber belt attached to the shaft that acts as a lift and carries the baggage from the lower level of the departure area till the basement through a chute.

Airport engineers said gaps between the rubber belts and the shafts were the primary reason for the system stalling. The motor bearings are also prone to glitches.

Sources blamed lack of supervision by the airport authorities for poor maintenance of the conveyor belts. "Maintenance is the issue. We have asked Siemens to carry out thorough maintenance and that is being done. We expect the problems to be solved in a fortnight," a senior airport official said.

A domestic flight usually has about 200 pieces of checked baggage. The number is more than 500 for an international airline operating larger aircraft.

A domestic airline usually deploys three workers to segregate the baggage according to flight. An international airline needs to have seven to eight persons for this task.

Airline officials said they have had to deploy double or even triple the number of workers for baggage operations because of conveyor belts malfunctioning.

"These frequent glitches are an inconvenience to airlines. We have requested the airport authorities to take immediate maintenance-related action that should be permanent in nature to mitigate frequent breakdown," said Captain Sarvesh Gupta, chairman of the airline operators' committee of Calcutta airport.