The Delhi airport authority has served notices to addresses of 176 obstacles, including a luxury hotel, a shopping mall, an electric traction system of Delhi Metro and trees, in the National Capital Region that pose threat to planes taking off or landing at the airport, PTI reported on Friday.

The Delhi International Airport Limited issued the notices following a directive of the Delhi High Court on July 30. These structures reportedly infringe a height restriction. Some of the buildings that have been served notices are Ambience Mall in Gurugram and the hotel Jaypee Vasant Continental in New Delhi.

“If the approach path of a flight is not clear, it is obviously a safety issue,” VK Kukar, a former Air India pilot told the Hindustan Times. “But whether a building is an obstacle has to be calculated through the distance and height [of a structure], and the height of an approaching plane in that area. There is a set formula for that and there is a possibility that some buildings might have come much later without the approval.”

According to the Ministry of Civil Aviation (Height Restrictions for Safeguarding of Aircraft Operations) Rules, 2015, any construction coming up within 20 km of an airport has to obtain a no-objection certificate from the Airports Authority of India.

An unidentified official of the Directorate General of Civil Aviation told the Hindustan Times that the regulator had issued orders asking owners of the obstacles to submit a plan to the airport authority showing “location, height of the structure, date of construction, distance from aerodrome reference point and any other relevant details”. If the owners fail to remove the obstacles, the Directorate General of Civil Aviation will initiate demolition of the structures, the official added.