It's not just commercial pilots in the United States reporting a growing number incidents with small drones, as a pilot in the UK flying into Heathrow Airport said he saw a drone flying close to the airport. The pilot of the Airbus 320 airliner estimates the drone was about 700 feet off the ground, with the UK Civil Aviation Authority issuing it a Class A (serious risk of collision) labelling.
The UK doesn't allow drones less than 44 pounds to go above 400 feet in elevation, and they cannot fly near commercial airspace and airports. However, it's possible private drone operators might not be aware of the restrictions - and are unaware of potential dangers.
Trying to prevent incidents between small drones and airliners is being left up to national governments, though they are responding slowly. Both the US and British governments are considering safety rules for airspace around airports, which would hold drone operators accountable for flying safely.