The Tamil Nadu government is in the process of finalising a consultant to conduct an Obstacle Limitation Surface (OSL) survey for the proposed Hosur Airport. The OSL is conducted to ascertain the air space in the region, which is controlled by the Ministry of Defence.

OSL survey covers a radius of up to 20 km from the proposed runway's reference point and uses modern equipment to measure the height and location of obstacles. Both proposed sites are near sensitive defence-controlled airspace, as Bengaluru is home to Hindustan Aeronautics Limited.

The development comes after the Airports Authority of India (AAI) found both sites - villages close to the private airport owned by Taneja Aviation and Aerospace Limited (TAAL) in Belagondapalli, and another near the Chennai-Bengaluru highway - as suitable for building the greenfield airport.

According to reports, the Tamil Nadu government has already written to the Defence Ministry seeking permission for relaxation of the airspace in Hosur for commercial operations. 

The AAI, in its report, spoke about the merits and demerits of both the locations shortlisted from five locations proposed by the Tamil Nadu government after it announced plans to construct a greenfield airport in Hosur.

In a parallel development, the TN government is also in touch with TAAL to convert its facility into Hosur Airport through a joint venture to develop the airport. One of the shortlisted sites is adjacent to the TAALairport.