At Hyderabad airport, you buckle into your seat for the late afternoon flight back to Delhi. The flight indicator tells you that Delhi is due north. It will be a straight flight, you believe. No time lost. You silently thank India's revolution in civil aviation.

Wrong! In the cockpit, the pilot has set course south instead of north. Flying in wide circles south of Hyderabad, he climbs to 20,000 feet before seemingly heading for Goa. Ninety kilometres later he will move towards Pune, covering another 100 km before finally heading for Delhi.

These inefficient diversions of civil flights at Hyderabad are caused because the airport is bordered by a vast swathe of restricted airspace belonging to the Indian Air Force flying academies of Hakimpeth and Bidar.

By the time you reach Delhi you will have flown an extra 20 minutes, and the airline will have spent Rs 40,000 extra as fuel cost. This wastage of time, fuel and money is eventually borne by the traveller.

The problem is not confined to Hyderabad. Almost half of India's airspace belongs to the military. The country is dotted with IAF fighter, helicopter and transport bases, training facilities, manufacturing units and design establishments. Each of them was allotted thousands of square kilometres of surrounding airspace at a time when civil flights were few and far between.

Civil aviation officials have not been able to persuade the IAF to loosen airspace restrictions despite dramatically changed circumstances.

Airports Authority, IAF on collision course

Says Ajay Prasad, secretary, Ministry of Civil Aviation, "The problem did not come into sharp focus as it is today. Now, with this expanding fleet, opening new routes and bringing new cities into the air map, the need for opening up the airspace has become much more important.

"It will cut distances short and save flying time because instead of making detours you will be able to fly in more of a straight line."

The Airports Authority of India, responsible for air traffic management around civil airports and civilian air routes, has been working with the IAF route by route, in an attempt to straighten domestic and international air routes.

Under pressure from the International Civil Aviation Organisation, the IAF agreed to straighten seven international routes, but it has not allowed a single domestic flight to fly unencumbered through its vast airspace holdings.

AAI Chairman K Ramalingam says, "We would like the Air Force to be more pro-active on restructuring air routes. We have urged them to release the airspace to us when they are not using it."

The IAF explains that it has several reasons for such restrictions. Without separate airspace, its highly agile aircraft, with flight patterns of rapid, unexpected climbs and manoeuvres, will be a serious hazard to civil airliners in the vicinity.

In several cases, the IAF has allowed civil flights to use its airspace provided they remain above 20,000 feet, the ceiling for fighter and helicopter flying.

But dividing airspace by altitude doesn't solve the problem. In cases like Hyderabad, Bangalore and even Delhi, the IAF's airspace is so close to the airport that civil flights enter it before they can climb to 20,000 feet.

Civil aviation authorities have come up with a proposal for "flexible use of airspace", in which the IAF would freely allow civil flights into its restricted airspace when IAF aircraft are not actually using it. Top IAF officers, however, dismiss the idea of "time-sharing".

A series of expert committees on airspace issues, such as the Roy Paul Committee, the Khola Committee and, most recently, the Naresh Chandra Committee in October 2004, have pushed for flexible use of airspace.

The IAF's reaction to these recommendations mirrors the polarisation on airspace issues between the civil aviation ministry and the Air Force.

Senior IAF officers dismiss the recommendations, asking why the Naresh Chandra Committee does not include an IAF representative.