The May scorcher has hit airlines having operations in the city economically.

The high temperature and the short runway at Jaiprakash Narayan International Airport are compelling the airlines to leave seats vacant in planes to comply with the load penalty factor. Operating below the capacity, they are incurring losses in the peak summer holiday season. The airlines operating older aircraft are the worst-hit.

Sources in Jet Airways have confirmed that it has curtailed the seating capacity in its planes on all routes from the city. The private airline operates older aircraft like ATR 72-500 (around 70 seats) and Boeing 737-700 (around 135 seats) from the city.

Air India, which usually operates Airbus 320 from the city, has switched to comparatively newer generation Airbus 319 in the sector to tackle the load penalty factor.

The load penalty factor comes into play when the temperature is 40°C or above. Generating high lift during take-offs becomes difficult under such circumstances because the air pressure remains low. (See graphic)

“The planes’ engines have to create a certain minimum thrust while taking off. As the air becomes thinner during summer, the pilots prefer to reduce the aircraft load for safe take-off from short runways so that the necessary engine thrust is available. Engines require less thrust when the planes are lighter. That is why flights do not operate with the capacity load during the summer months, especially in the daytime,” said a source in the aviation industry.

Weathermen said the temperature in the city at this time of the year veers around 40°C and above. “The maximum temperature around mid-May is normally 40°C and above and a rising trend is observed till the second week of June,” said Ashish Sen, the director of India Meteorological Department, Patna.

The load penalty factor plays a major role at Patna airport because of its short runway. Against the total runway length of 2,286m (7,500 feet), only 1,954m (6,409 feet) remains available to pilots at the time of take-off because of the location constraint of the airport.

“When the load penalty factor comes into play in Patna, the airlines like Jet Airways and Air India, which mostly operate aircraft of older generations, are left with no option than to either restrict ticket booking or offload few passengers prior to take-off to reduce the weight of the aircraft. At times, the airlines carry the baggage in earlier flights and passengers are asked to take the next flight on a particular route,” said a source at Patna airport.

The source in the aviation industry confirmed that the load penalty factor has economic implications on the airlines. “The load penalty is highest for ATR aircraft. If 20 seats are left vacant in a flight on the Patna-Calcutta route, the loss would amount to around Rs 4,000 per seat,” said the source.

He said the implication becomes more pinching because a lot of people travel in May and June.