From London proper, it's best to take the train to the airports. If you're lucky you're flying out of London City Airport, but most of the time I'd go to Gatwic

From London proper, it's best to take the train to the airports. If you're lucky you're flying out of London City Airport, but most of the time I'd go to Gatwick or Heathrow by train and it's a good way to get there.