This was done to allay security concerns as it was feared that sabotage activities could be undertaken to target runways and VVIP operational areas from these buildings.
Samples of the bulletproof glass was recently tested by a team of the Defence Research and Development Organisation in Chandigarh in the presence of a technical specification committee comprising officials from intelligence and security agencies and Bureau of Civil Aviation Security.
"Bullets were fired on the glass sheet to test their effectiveness. A few meters behind the glass an aircraft frame was kept to examine the possible impact if a bullet was fired from inside the hotel room," a top official of the Delhi International Airport Limited (Dial), the private operator of the Delhi airport, said.
In all, the official said, 12 tests were done, and bullets after hitting the glass, could hardly go up to 10-15 metres. "The runway is 400 metres from the hotel while the airside is 250 metres. We expect that the report would soon be submitted and there would be no more delays in the opening of the hotels," the Dial official added.