Flying time to London is about 6½ hours from New York, 7½ hours from Chicago, 11 hours from San Francisco, and 21½ hours from Sydney.
For flights out of London, the general rule is that you should be at the airport at least one hour before your scheduled departure time for domestic flights and two to three hours before international flights.
Most international flights to London arrive at either Heathrow Airport (LHR), 15 miles west of London, or at Gatwick Airport (LGW), 27 miles south of the capital. Most flights from the United States go to Heathrow, which is divided into five terminals, with Terminals 3–5 handling transatlantic flights. Gatwick is London's second gateway. It has grown from a European airport into an airport that also serves dozens of U.S. destinations. A third airport, Stansted (STN), is 35 miles northeast of the city; it handles European and domestic traffic. Three smaller airports, Luton (LTN), 30 miles north of town, Southend (SEN), 40 miles to the east, and business-oriented London City (in east London E16) mainly handle flights to Europe.
London has excellent if pricey bus and train connections between its airports and central London. If you're arriving at Heathrow, you can pick up a map and fare schedule at the Transport for London (TfL) Information Centre, in the Underground station serving Terminals 2–3. Train service can be quick, but the downside (for trains from all airports) is that you must get yourself and your luggage to the train via a series of escalators and connecting trams. Airport link buses (generally National Express airport buses) may ease the luggage factor and drop you off closer to central hotels, but they're subject to London traffic, which can be horrendous and make the trip drag on for hours. Taxis can be more convenient than buses, but beware that prices can go through the roof. Airport Travel Line has additional transfer information and takes advance booking for transfers between airports and into London.
Heathrow by Bus: National Express buses take one hour to reach the city center (Victoria) and cost from £6 one-way and £12 round-trip (book online for best prices). The National Express Hotel Hoppa service runs from all airports to 25 hotels near the airport (from £4.50). Heathrow Shuttle offers a shared minibus service between Heathrow and more than 500 London hotels starting from £15. The N9 night bus runs to Aldwych every 20 minutes midnight–5 am; it takes just over an hour and costs £1.50 (you need to pay with an Oyster card or a contactless debit/credit card). Please note: the N9 doesn't stop at Terminal 4; take Bus Nos. 490 or 482 to Terminal 5 and catch it there.
Heathrow by Tube and Train: The cheap, direct route into London is via the Piccadilly Line of the Underground (London's extensive subway system, or "Tube"). Trains normally run every four to eight minutes from all terminals from early morning until just before midnight. The 50-minute trip into central London costs £6 one-way and connects with other central Tube lines. The Heathrow Express train is comfortable and convenient, if costly, speeding into London's Paddington Station in 15 minutes. Standard one-way tickets cost £22 (£37 round-trip) and £32 for first class. Tickets are more expensive to buy on board, so book ahead (online is the cheapest option; at a counter/kiosk, less so). There's daily service 5:10 am (6:10 am on Sunday)–11:25 pm, with departures usually every 15 minutes. Local trains to Paddington are a cheaper alternative to the Heathrow Express (one-way tickets start from £10.50). However, these trains take a little longer (28 minutes), are less frequent (two per hour), and make five stops en-route. They also have no first class carriages.
Heathrow by Taxi: Taking a taxi from the airport into the city is an expensive and time-consuming option. The city's congestion charge (£11.50) may be added to the bill if your hotel is in the charging zone; you run the risk of getting stuck in traffic; and if you take a taxi from the stand, the price will be even more expensive (whereas a minicab booked ahead is a set price). The trip can take more than an hour and can cost in the region of £70, depending on time of day.
Gatwick by Bus: An hourly bus service runs from Gatwick's north and south terminals to London's Victoria Station, with stops at Hooley, Coulsdon, Mitcham, Streatham, Stockwell, and Pimlico. The journey takes upward of 90 minutes (depending on time of day) and costs from £5 one-way. The easyBus service runs to west London (Earl's Court) or Waterloo from as little as £2 if booked in advance; the later the ticket is booked online, the higher the price (up to £11 on board).
Gatwick by Train: The fast, nonstop Gatwick Express leaves for Victoria Station every 15 minutes, 6 am–11:10 pm. The 30-minute trip costs from £19.90 one-way, and £35 round-trip (cheapest tickets are available online). The Thameslink Great Northern rail company runs nonexpress services that are cheaper; Thameslink trains run regularly throughout the day to St. Pancras International, London Bridge, and Blackfriars stations; departures are every 15 minutes (hourly during the night), and the journey takes 45–55 minutes. Tickets are from £9.70 one-way to St. Pancras International.
Stansted by Bus: Hourly service on National Express Airport bus A6 (24 hours a day) to Victoria Coach Station costs from £5 one-way, £10 round-trip, and takes about 1 hour 45 minutes (again, the cheapest tickets are only available online and in advance). Stops include Golders Green, Finchley Road, St. John's Wood, Baker Street, Marble Arch, and Hyde Park Corner. The easyBus service to Victoria via Baker Street costs from £2 one-way, but book early and online for best prices.
Stansted by Train: The Stansted Express to Liverpool Street Station (with a stop at Tottenham Hale) runs daily every 15 minutes, 5:30 am–12:30 am. If booked online, the 50-minute trip costs from £7 one-way and £14 round-trip; tickets cost more when purchased on board or nearer travel time.
Luton by Bus and Train: An airport shuttle runs from Luton Airport to the nearby Luton Airport Parkway Station, from which you can take a train or bus into London (this shuttle is free if you have bought a rail ticket in advance; otherwise it's £2.40 one-way). From there, the Thameslink Great Northern train service runs to St. Pancras, Farringdon, Blackfriars, and London Bridge. The journey takes about 30 minutes. Trains leave every 10 minutes or so during the day, and hourly during the night. Single tickets cost from £13 one-way, if booked in advance. The Green Line 757 bus service from Luton to Victoria Station runs three times an hour, takes about 90 minutes, and costs from £11 one-way, if booked in advance.
Transfers Between Airports
Allow at least two to three hours for an interairport transfer. The cheapest option—but most complicated—is public transportation: from Gatwick to Stansted, for instance, you can catch the nonexpress commuter train from Gatwick to Victoria Station, take the Tube to Liverpool Street Station, then catch the train to Stansted from there. To get from Heathrow to Gatwick by public transportation, take the Tube to King's Cross, then change to the Victoria Line, get to Victoria Station, and then take the commuter train to Gatwick.
The National Express airport bus is the most direct option. Between Gatwick and Heathrow, buses pick up passengers every 15–20 minutes 3.15 am–midnight from both airports. The trip takes around 75 minutes, and the fare is from £27 one-way, but it's advisable to book tickets in advance. National Express buses between Stansted and Gatwick depart every 30–45 minutes and can take 3–4½ hours, depending on traffic. The adult one-way fare is from £19. Some airlines may offer shuttle services as well—check with your travel agent in advance of your journey.