Heathrow is London's main hub airport. However, it is also incredibly busy and can be crowded and frustrating, and the botched opening of Terminal 5 did not help. Gatwick is a nicer place to arrive, and City airport is the best for the business community - though both take longer to get to the western part of London.
How to Arrive via Heathrow
Heathrow Express
The Heathrow Express is a non-stop service that goes directly to Paddington Station on the Underground. Prices range from £15.50 to £24.50 for a single journey, standard class and first class respectively. Trains leave from all 5 terminals every 15 minutes.
Heathrow Connect
Heathrow Connect goes to Paddington along the same route as Heathrow Express, but makes stops at 5 other National Rail stations along the way, including Ealing Broadway, West Ealing, Hanwell, Southall, and Hayes & Harlington. Trains leave the Paddington every 30 minutes and stop at Terminals 1-4. Heathrow Connect is cheaper than Heathrow Express, costing only £6.50 and having a journey of 25 minutes.
Underground
To use the Underground, Heathrow has services from the Piccadilly Line, with 4 stops at the terminals serving the airport. Ticket machines and ticket offices are available in each station, where you can purchase tickets or an Oyster Card.
National Express
For longer distances outside of London, National Express has several coaches that travel to other areas of the UK. Several buses leave from Heathrow and make stops at Stansted, Luton, and Gatwick, along with cities outside of London, like Bristol and Cardiff.
RailAir
RailAir coach is also a service that provides non-stop bus connections to other railway services in the UK. Tickets one way cost £14 pounds without a Railcard.
How to Arrive via Gatwick
Gatwick Airport Railway Station
The Gatwick Airport Railway Station is one of the many ways to travel to and from the airport. It provides various connections to London Victoria and London Bridge Stations and Brighton. Trains operate every 15 minutes from the airport toward Victoria station. The best train to take - though a bit more expensive at £17 than the regular stopping service, is the Gatwick Express.
National Express
National Express also has coach services to Heathrow and Stansted.
How to Arrive via City Airport
Docklands Light Railway
Via the Docklands Light Railway, which connects to the London City airport, it is possible to change at various stations on the London Underground. All-day "Rover" tickets will give you access to the DLR an all its stations. Oyster Cards are also available for use on the DLR and give you access to bus and Underground transportation as well.
Buses
Buses 473 and 474 also run in different locations in East London. 473 Bus runs from the airport via Prince Regent Lane, and Plaistow and Stratford tube stations. In the opposite direction, the 473 heads toward Albert Road, ending at North Woolwich, where there is a ferry and a foot tunnel to cross the Themes. The 474 runs toward Beckton and Cyprus, ending at East Ham and Manor Park. In the other direction from the airport, the 474 stops at North Woolwich Road, toward Canning Town tube station and Barking Road.