London's Heathrow airport, the busiest aviation hub of Europe, yesterday suspended all departing flights for a brief period following reports of a drone sighting. In a similar incident three weeks back, about 1,000 flights were grounded at the Gatwick airport. <br />''<br />''Around 81 airlines serving 204 destinations operate out of Heathrow airport, located west of London. Arriving planes, however, continued to land at the airport.<br />'' <br />''The latest incident came few days after both the airports reportedly invested significant amount of money in military-grade anti-drone technology.<br />