WHEELING, Ill. (WLS) -- Residents in the Northwest suburbs have been alerted to the threat drones can be to air traffic after two close calls at Chicago Executive Airport in Wheeling.With over 77,000 take-offs and landings a year, Wheeling's Chicago Executive Airport, formerly Palwaukee Airport, is the fourth busiest in Illinois. So, when a drone was found lying on the grass near the airfield, airport officials became very concerned."We think someone tried to maliciously cross the airfield and ran out of a battery or lost signal and the drone dropped in middle of the airfield," said Bryce Walter of the Chicago Executive Airport.That incident happened back in November. Another drone was spotted in March on the north end of the airport's busiest and main runway.The FAA requires drone users - hobbyists and professionals - to notify an airport if they are flying within in five miles of the airport. With two near misses within four months at Chicago Executive Airport, officials know the next time could be devastating."A drone hitting a cockpit window could shatter it and potentially kill both pilots inside and take out an engine. It could bring a plane down," said Walter.To make sure that never happens, the airport has launched a campaign notifying drone hobbyists of the rules, especially since drones are getting more popular as the prices have dropped. The drone found on the airfield in November sells for less than $100. The airport has posted no fly signs around the perimeter of the airport and in local parks.Commercial drone operators are also pushing for drone hobbyists to follow the FAA rules.As drones become more popular, sightings near airports or airplanes go up. The FAA says there are more than 100 nationwide. Fortunately, there have not been any collisions in the United States, but many say it is only a matter of time.