I had heard of it but had assumed that it was another name for Heathrow. Not so, as Hidden London explains:
In 1919 Hounslow Heath became the site of the first civil airport in the country. The earliest commercial flight was from Bristol to Hounslow and the inaugural scheduled air service was from Hounslow to Paris. On 12 November the first flight to Australia left Hounslow, arriving 28 days later. Commercial aviation moved to Croydon in 1920 and the airport closed. Its buildings were destroyed by fire in 1929 but a plaque in Staines Road marks the site.