Three cases of drone sightings in the last two weeks including one near the Parliament have kept Delhi Police on their toes.The security control room at Delhi airport received three calls of drone sighting from three different parts of the city in the last couple of weeks, none of which could be located later.On September 17 around 10pm, the Delhi police security control room was informed about the sighting of a drone like object in the Parliament area. The air traffic controller at Delhi airport was asked to check the radar but drone movements are usually not captured on the ATCs radar. However, security personnel were alerted,said an official of Central Industrial Security Force CISF, requesting anonymity.Airport official said that every month, nearly 6 to 7 cases of pilots getting distracted by different objects are reported from near the airport, but security agencies are yet to find a clue in any of the cases.